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### DDBlock

## Silicon qubit fidelities approaching stochastic noise limits via pulse optimisation

Speaker:

Dr Henry Yang
From:

CQC2T at UNSW
When:

4pm Thursday 17 May 2018
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus To achieve a fault-tolerant quantum computing system, it will be necessary to further improve single qubit gate fidelities to reduce the overhead for quantum computing. In this talk, we show that by employing GRAPE computed optimised control pulse shaping scheme and other calibration techniques, we can improve average Clifford gate fidelities for silicon quantum dot spin qubits by an order of magnitude, to 99.96% (equivalent coherence time of 9.4ms) experimentally, the highest up to date record in silicon quantum dot qubits.

## Anisotropy and inhomogeneity of the magnetic properties of individual erbium ions in silicon

Speaker:

Dr Gabriele De Boo
From:

CQC2T at UNSW
When:

4pm Thursday 3 May 2018
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus Long coherence times can be achieved by using the spin states of the rare earth ion erbium. These spin states are accessible with optical transitions, which provides possibilities for long range coupling of these states. We investigate the magnetic properties of single erbium ions in silicon in order to identify suitable ions for quantum communication. Our results show that the individual ions have highly anisotropic Zeeman splittings which vary from ion to ion.

## Building a quantum computer using silicon/silicon-germanium heterostructures

Speaker:

Prof Susan Coppersmith
From:

University of Wisconsin-Madison
When:

4pm Thursday 10 May 2018
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus In principle, quantum computers that exploit the nature of quantum physics can solve some problems much more efficiently than classical computers can. Motivated by the tremendous scalability of classical silicon electronics, a group of us at University of Wisconsin-Madison are working to build a large-scale quantum computer using silicon/silicon-germanium quantum dots, constructed using technology similar to that used to build current classical computers.

## Quantum Hall Effect: True microscopic picture and tuning its edge regime

Speaker:

Mr Rostyslav Savytskyy
From:

CQC2T at UNSW
When:

4pm Thursday 26 April 2018
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus The Quantum Hall Effect (QHE) was discovered in 1980 and many works have been published since then related to the Physics of this phenomenon. However, there still exists misconception about its microscopic picture in the form of the dissipationless 1D current-carrying edge-states. Thus, I will present scanning probe microscopy measurements conducted at the von Klitzing department (MPI Stuttgart), which have demonstrated the actual current distribution inside the Hall sample during QH plateau [1].

## Development of 3D P in Si quantum computing architecture for error correction

Speaker:

Mr Mitchell Kiczynski
From:

CQC2T at UNSW
When:

4pm Thursday 19 April 2018
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus Phosphorus donor devices in silicon fabricated using STM hydrogen resist lithography are typically fabricated in a 2D design using a single lithographic layer. However in order to achieve quantum error correction with a surface code architecture we need to be able to fabricate devices in three dimensions using multiple lithographic layers [1]. Here I will present on the fabrication challenges associated with transitioning from single layer devices to a multilayer structure and the techniques we used to overcome these challenges, allowing for the fabrication of high quality multilayer devices.

## Reaching beyond the horizon of classical computation: how to measure and improve the quantum capacity for computation

Speaker:

Prof. Joseph Emerson
From:

Institute for Quantum Computing & Department of Applied Mathematics, University of Waterloo, Canada
When:

4pm Friday 13 April 2018
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus I will present some recent breakthrough theoretical results to identify and suppress errors across a quantum computer in an efficient and practical manner. I will also present preliminary results on the implementation of these methods on a 10 qubit ion trap quantum computer.

## Two qubit randomized benchmarking of quantum dot spin qubits

Speaker:

Mr Wister Huang
From:

CQC2T at UNSW
When:

4pm Thursday 12 April 2018
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus Qubits encoded in the electron spin states of gate-defined quantum dots are promising because of their long coherence time. Recent experiments have realized both single qubit operations with fault-tolerant fidelity [1-2] and two qubit logic gates [3-5]. For single qubit gates, randomized benchmarking has emerged as a popular characterization tool. However, for two-qubit gates it has so far only been applied to a few qubit implementations.

## High sensitivity spin measurements in atomic precision devices

Speaker:

Dr Matthew House
From:

CQC2T at UNSW
When:

4pm Thursday 5 April 2018
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus In order to achieve fault-tolerant quantum computation we must meet a very demanding set of requirements, including a very low error rate for qubit readout, much less than 1%. The error rate for ancilla qubit readout includes decoherence of data qubits that occurs during the readout time, which means that readout must be not just accurate, but also much faster than the qubit T2 time.

## Recent results in spin-photon coupling from Princeton and Delft

Speaker:

Dr Sacha Kocsis
From:

CQC2T at UNSW
When:

4pm Thursday 15 March 2018
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus Two high-profile results on coupling the spin of gate-defined quantum dots to superconducting microwave resonators have recently been published. I will review the 2018 papers from groups at Princeton ["A coherent spin-photon interface in silicon", doi:10.1038/nature25769] and Delft ["Strong spin-photon coupling in silicon", doi:10.1126/science.aar4054].

## Quadrupole-induced electrical control of a single 123-Sb nucleus

Speaker:

Mr Serwan Asaad
From:

CQC2T at UNSW
When:

4pm Thursday 8 March 2018
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus The 123-Sb atom is a group-V element with a nuclear spin quantum number of 7/2, resulting in an 8-dimensional Hilbert space. This atom can be implanted in a silicon Metal-Oxide-Semiconductor structure, and its quantum state can be controlled using the same infrastructure that has been proven to yield high-fidelity control and single-shot readout on the 31-P donor.

## Single donors in highly strained silicon

Speaker:

Dr Benoit Voisin
From:

CQC2T at UNSW
When:

4pm Thursday 1 March 2018
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus Strain is a common ingredient in solid-state systems which has been widely used to enhance electronic devices performances, both electrically and optically, via a change in the band structure of materials. Consequently, strain also induces a change in the properties of single dopants, and schemes have now emerged to use strain to define or tune qubits for quantum technology purposes. Ensemble measurements of donors in strained silicon have been carried out, but yet to date no experiment down to the single atom level has been performed.

## Engineering long spin coherence times of holes in silicon

Speaker:

Dr Joseph Salfi
From:

CQC2T at UNSW
When:

4pm Thursday 22 February 2018
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus Future quantum technologies require quantum bits that remain coherent over long time scales, a goal recently achieved for electron spins in some semiconductors. Because of their strong spin-orbit coupling, hole-based qubits have attracted interest to achieve long-distance coupling, and to build hybrid quantum systems and spin/photon interfaces. However, it is not known if spin-orbit coupling of holes is compatible with long coherence times, since to date, experimentally reported values are too short for most envisioned applications.

## High fidelity control and coherence of two-electron spin qubits in GaAs quantum dots

Speaker:

Dr Tim Botzem
From:

CQC2T at UNSW
When:

4pm Thursday 15 February 2018
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus I will present our method to experimentally realize high-fidelity single qubit operations for a qubit encoded in two electron spins in GaAs quantum dots by iterative tuning of the all-electrical control pulses. We find an average gate fidelity of F = 99.5% and determine gate leakage out of the computational subspace to L = 0.04%. These results demonstrate that high fidelity gates can be implemented even in the presence of nuclear spins.

## Probing the non-linear dispersive response of a strongly driven quantum dot at gigahertz frequencies

Speaker:

Mr Mark Hogg
From:

CQC2T at UNSW
When:

4pm Thursday 7 December 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus Minimizing the number of physical gates required for control of semiconductor spin qubits is an important problem. A promising strategy is to use rf reflectometry with “gate-based” charge sensing for qubit readout. Studies to date have focused on charge sensing performance in the regime of weak rf driving where the response is linear, but when driven strongly the admittance of a quantum dot saturates to a constant ac current due to Coulomb blockade.

## Characterisation of a scalable donor based singlet-triplet qubit architecture

Speaker:

Mr Prasanna Pakkiam
From:

CQC2T at UNSW
When:

4pm Thursday 30 November 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus We present a donor based quadruple quantum dot device, designed to host two singlet-triplet qubits fabricated by scanning tunnelling microscope lithography, with just two leads per qubit. The design is geometrically compact with each pair of dots independently controlled via one gate and one reservoir. The reservoirs both supply electrons for the dots and measure the singlet-triplet state of each qubit via dispersive sensing. We verify the locations of the four phosphorus donor dots via an electrostatic model of the device.

## Readout Of Singlet-Triplet Spin Qubits At Large Magnetic Field Gradients

Speaker:

Mr Lucas Orona
From:

Harvard University
When:

4pm Thursday 23 November 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus Singlet-triplet qubits are one particularly successful implementation of spin qubits that has recently demonstrated improved immunity to charge noise by applying intense magnetic field gradients. However, large magnetic field gradients allow for relaxation between qubit states during measurement, reducing readout visibility to almost zero. Here we present a new technique that is robust against these relaxation pathways and enables working above magnetic field gradients of 400 MHz, a regime that unaccessible using previously studied methods.

## Modelling Exchange in Silicon Quantum Dots

Speaker:

Mr Brandon Buonacorsi
From:

Institute for Quantum Computing at the University of Waterloo, Canada
When:

2pm Friday 17 November 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus A challenge for modelling quantum dot spin qubits in silicon is the quantitative estimation of the exchange energy J over a wide range of electrostatic potentials. Approximate methods such as Heitler-London and Hund-Milliken are often applied to GaAs dots, but break down in silicon due to the larger effective mass of the electron. I will discuss our progress towards building a simulation toolbox for exchange energies based on configuration interaction (CI) methods commonly used in quantum chemistry.

## High Bandwidth Electron Spin Readout with the Radio Frequency Single Electron Transistor

Speaker:

Mr Daniel Keith
From:

CQC2T at UNSW
When:

4pm Thursday 2 November 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus Qubit state readout is an essential step for quantum computation and must introduce minimal errors if full error correction is to be achieved with a surface code architecture. The lowest errors during readout will only be possible if the readout is not only high fidelity, but also high bandwidth. Typically, for electron spin qubits in Si-P donor based systems, a single electron transistor (SET) is used as a charge sensor to perform single-shot electron spin readout.

## Shell structure and spin filling of the first six holes in a silicon MOS quantum dot

Speaker:

Mr Scott Liles
From:

School of Physics at UNSW
When:

4pm Thursday 26 October 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus Heavy hole spins in quantum dots are promising candidates for spin qubits. This is because holes have reduced hyperfine coupling to nuclear spins, allowing long spin coherence times [1], while the enhanced spin-orbit coupling of holes enables fast all-electric spin manipulation via EDSR [2]. However, challenges in device fabrication and complexities in theory have limited the number of studies using hole-based devices. In this talk we discuss our recent progress in silicon-based hole quantum dots.

## Layout-Aware Embedding of Quantum-Dot Cellular Automata Networks onto a D-Wave Quantum Annealer

Speaker:

Mr Jose Pinilla
From:

University of British Columbia, Vancouver, Canada
When:

4pm Thursday 5 October 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus Advancements in Quantum-dot Cellular Automata (QCA) fabrication have posed this technology as an alternative to CMOS for general-purpose computing. Reliable simulation of QCA circuits requires computation of the ground state and dynamics of the complete quantum mechanical formulation, which becomes computationally infeasible with increasing problem sizes. In this paper, we present an embedding algorithm which maps a QCA circuit to a D-Wave Quantum Annealing Processor to allow for efficient ground state computation.

## Understanding plasmonic waveguides for nanoscale nonlinear interactions

Speaker:

Dr Guangyuan (Clark) Li
From:

The University of Sydney
When:

4pm Thursday 28 September 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus Many processes in quantum information science rely on nonlinear optical interactions. In this talk, we will present our progress in Kerr nonlinear plasmonics. I will first discuss the advantages and challenges of using plasmonics for nanoscale nonlinear applications. In order to quantify the ultimate nonlinear performance and compare different plasmonic waveguides, we propose a versatile figure of merit. We also provide a deep understanding to the ultimate nonlinear performance.

## Coherent electron spin control in atomically precise donor systems

Speaker:

Mr Ludwik Kranz
From:

CQC2T at UNSW
When:

4pm Thursday 21 September 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus In this talk we will discuss the progress in precision donor qubits in silicon. We will demonstrate the successful integration of a microwave transmission line onto two few electron double donor dot devices in silicon fabricated with the atomic precision of a scanning tunneling microscope (STM). The transmission line is used for magnetically driven Electron Spin Resonance (ESR) and a DC-coupled SET charge sensor is employed for single-shot spin readout. In the first device we use ESR spectroscopy to identify the characteristic hyperfine spectra of a single donor 1P and two-donor 2P dots.

## Strain detection using a single erbium atom in silicon

Speaker:

Dr Chunming Yin
From:

CQC2T at UNSW
When:

4pm Thursday 14 September 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus As the size of microelectronic devices approaches fundamental limits, their performance is strongly influenced by the local environment inside the device, such as electric field and strain. Here we present the effect of applied strain on single erbium ions in a silicon transistor. This result, in conjunction with the Stark effect detection demonstrated previously, can be utilised for non-destructive 3D imaging of the local strain and electric field in nano-transistors, using the single erbium ions as atomic sensors.

## Optimization of spin readout fidelity by counting statistics in a phosphorus donor device

Speaker:

Dr Yu He
From:

CQC2T at UNSW
When:

4pm Thursday 10 August 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus We investigate spin and charge dynamics of a quantum dot of phosphorus atoms coupled to a radio-frequency single-electron transistor (rf-SET) using full counting statistics and inverse counting statistics.

We show how the magnetic field plays a role in determining the bunching or anti-bunching tunnelling statistics of the donor dot and SET system. Using the counting statistics we show how to determine the lowest magnetic field where spin-readout is possible. We then show how such a measurement can be used

to investigate and optimise single electron spin-readout fidelity.

## Supercurrent transistors, hole quantum dots and defects in silicon systems

Speaker:

Dr Floris Zwanenburg
From:

The University of Twente
When:

2:15pm Friday 28 July 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus First, I will present results on semiconducting Ge/Si core/shell nanowires: In double quantum dots, we observe shell filling of new orbitals and corresponding Pauli spin blockade. In nanowires with superconducting Al leads we create a Josephson junction via proximity-induced superconductivity. A gate-tuneable supercurrent is observed with a maximum of ~60 nA. We identify three different regimes tuneable via backgate voltages: Cooper pair tunnelling, quasiparticle transport and finally full suppression of transport.

## Singlet-triplet readout in Si quantum dots based on (2,1)-charge state

Speaker:

Dr Tuomo Tanttu
From:

CQC2T at UNSW
When:

4pm Thursday 20 July 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus Singlet-triplet readout of two nearest neighbor quantum dots is an essential tool for scaling up quantum computing in silicon MOS systems [1]. Traditionally this parity readout is done in (2,0) charge configuration of a double quantum dot systems where triplet states are blockaded in (1,1) state due to Pauli exclusion principle. This difference in the charge configuration can be detected with a charge sensor only if the two dots have sufficient differential capacitance to the sensor.

## A room-temperature noise-free quantum memory

Speaker:

Dr Dylan Saunders
From:

University of Oxford Department of Physics
When:

4pm Thursday 13 July 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus Light combines the ability to carry quantum information in ambient conditions with a large information capacity, making it ideal for building quantum networks. However, due to the probabilistic nature of linear-optical entangling operations, it remains an outstanding challenge to grow such networks. Historically, the goal of swapping entanglement over large scale networks motivated the development of "quantum repeaters'', based on quantum memories that can trap and release photons on demand to synchronise entangling operations.

## High fidelity single-shot singlet-triplet readout of precision placed donors in silicon

Speaker:

Mr Samuel Gorman
From:

CQC2T at UNSW
When:

4pm Thursday 6 July 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus We perform direct single-shot readout of the singlet-triplet states in exchange coupled electrons confined to precision placed donor atoms in silicon. Our method takes advantage of the large energy splitting given by the Pauli-spin blockaded (2, 0) triplet states, from which we can achieve a single-shot readout fidelity of 98.4 +- 0. 2 %. We measure the triplet-minus relaxation time to be of the order 3 s at 2.5 T and observe its predicted decrease as a function of magnetic field, reaching 0.5 s at 1 T.

## Implementing Grover´s algorithm in molecular TbPc2 qudits

Speaker:

Prof Mario Ruben
From:

Karlsruhe Institute of Technology, Germany
When:

4pm Thursday 3 August 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus Magnetic metal complexes have been proposed as Qubits or Qudits (d = 2 or d > 2) candidates for Quantum Computing (QC) and Quantum Information Processing (QIP). Herein, we report on the implementation of metal complexes into nanometre-sized (single-) molecular spintronic devices by a combination of bottom-up self-assembly and top-down lithography techniques.

## Incorporating Dispersive Readout in SiMOS Architectures

Speaker:

Mr Anderson West
From:

CQC2T at UNSW
When:

4pm Thursday 29 June 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus Silicon Metal Oxide (SiMOS) based architectures are an excellent platform for single electron spin qubit systems. SiMOS systems possess long coherence times1, allow high fidelity control of electron spins1, and enable a two-qubit logic gate1. Current technology features spin control via electron spin resonance (ESR) and sensing is achieved via an on chip single electron transistor enabling single-shot reservoir spin readout. However, extending the SiMOS platform to a larger number of qubits will require an alternative readout mechanism.

## Sub-THz kinetic inductance bolometer arrays and cameras for security applications

Speaker:

Dr Andrey Timofeev
From:

CQC2T at UNSW
When:

4pm Thursday 22 June 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus Sub-THz imaging (0.1-1 THz) is an emerging technology for stand-off security screening of concealed objects in mass transit and public areas.

## Tuning the spin state of a single boron atom in silicon by electric field

Speaker:

Mr Guangchong Hu
From:

CQC2T at UNSW
When:

4pm Thursday 15 June 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus The spin degree of freedom of an acceptor in silicon provides an attractive alternative to the well-established donor spin qubit in silicon due to the potential to electrically manipulate the quantum state. Here we discuss the modification of the spin-orbit coupling of a hole trapped by a boron site in a silicon transistor based on electrical field

## Determining the site symmetry and crystal field splitting of individual erbium ions

Speaker:

Mr Gabriele De Boo
From:

CQC2T at UNSW
When:

4pm Thursday 8 June 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus The spin states of rare earth atoms such as erbium have long coherence times which makes them interesting for the use as quantum memories. These spin states can be accessed through optical transitions, with erbium having transitions at the convenient wavelength of 1540 nm. We use these optical transitions to study erbium’s spin states inside a silicon transistor in order to determine the local site symmetry as well as the crystal field splitting.

## Principal investigations of acceptor qubits in silicon

Speaker:

Dr Joost Van Der Heijden
From:

CQC2T at UNSW
When:

4pm Thursday 1June 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus While a number of breakthroughs have been made in donor-based qubit systems, the small dipole moment of donor spins makes inter-connection of many qubits challenging. Acceptor spins, on the other hand, possess spin-orbit coupling, which offers a spin qubit with a large electric dipole moment. However, static and dynamic properties of acceptor spins have yet to be unveiled in experiments. Towards realisation of an acceptor qubit, we investigate spin relaxation and spin coherence for two different kinds of spin level configurations of boron atoms, in both single atom and ensemble measurements.

## Robust electric dipole transition of a nuclear-spin in silicon

Speaker:

Dr Guilherme Tosi
From:

CQC2T at UNSW
When:

4pm Thursday 25 May 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus The nuclear spin state of a phosphorus donor in isotopically enriched silicon-28 (Si:P) is an excellent host to store quantum information in the solid state. The spin's insensitivity to electric fields yield a solid-state qubit with record coherence times, but also renders coupling to other quantum systems very challenging. I will show that, by coupling the phosphorus donor to an electron shared with an interface dot, a magnetic drive creates a strong electric dipole

## Pulse optimisation in a silicon quantum dot spin qubit

Speaker:

Dr Henry Yang
From:

CQC2T at UNSW
When:

4pm Thursday 18 May 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus Pulse optimisation has been implemented in system such as NMR to improve nuclear spin-readout fidelity. In this talk, we show that optimised microwave pulse calculated using GRAPE algorithm can improve our silicon spin qubit gate fidelities through simulation. Preliminary results of such optimised pulses that applied to our physical qubit will also be presented.

## Interface induced spin-orbit interaction in silicon quantum dots and prospects of scalability

Speaker:

Dr Kok Wai Chan
From:

CQC2T at UNSW
When:

4pm Thursday 11 May 2017
Where:

CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus Silicon (Si) quantum dots (QD) have been among the most prominent candidates for implementing spin based qubits with a potential for scalability, due to their exceptional coherence times and industry standard fabrication process. To build a large-scale quantum computer with Si QDs, we must address any dot-to-dot variations that can cause randomness in qubit operations.

## Atomic-Scale Engineering of Solid Interfaces:Towards Enhanced Electronic and Optoelectronic Functionalities

Speaker:

Dr Agustin E. Schiffrin
From:

Monash University
When:

4pm Thursday 4 May 2017
Where:

CQC2T Conference Room, Level 2 Newton Building, UNSW Electronics and optoelectronics technologies rely on the control of electric charge at the interfaces between active materials of solid-state devices. This behaviour is dictated by quantum mechanical phenomena unfolding at the nanoscale and depends strongly on the atomic-scale morphology of these systems.

## Cavity readout of single nuclear spin – Theory

Speaker:

Dr Vivien Schmitt
From:

CQC2T UNSW
When:

4pm Thursday 27 April 2017
Where:

CQC2T Conference Room, Level 2 Newton Building, UNSW Single implanted atoms in silicon are known to be extremely good individual qubits. A way to couple many of them together is to use a superconducting resonator, as extensively used for superconducting qubits.

In this presentation, I will present an intermediate step towards this objective: the theory of the readout of a single nuclear spin state, using a microwave cavity.

## Circuit Nano-Electromechanics

Speaker:

Dr Hans-Gregor Huebl
From:

Walther-Meißner-Institut, Garching, Germany
When:

4 pm Wednesday 19 April 2017
Where:

CQC2T Conference Room, Level 2 Newton Building, UNSW Micro- and nanomechanical elements are extensively studied due to their importance in force and mass sensing applications. To access their mechanical response, these vibrating elements are typically integrated into an electronic, electromagnetic, or optical environment. In cavity optomechanics, the interaction of a light field in an optical resonator with the mechanical degree of freedom goes beyond the sole readout functionality. Here, the light-matter interaction enables the manipulation of the mechanical state, manifesting itself e.g.

## Development of WSi superconducting single photon detectors

Speaker:

Dr Shouyi Xie
From:

CQC2T, UNSW
When:

4pm Thursday 13 April 2017
Where:

CQC2T Conference Room, Level 2 Newton Building, UNSW Single photon detectors are essential elements in the field of quantum optics. Amongst all the existing detector technologies, superconducting single photon detectors (SSPDs) based on WSi material turned out to be promising due to their high efficiency at near infrared wavelengths, fast recovery time, low timing jitter and low dark count rate. Moreover, the as-deposited WSi film is amorphous and highly uniform. The fabricated devices thus show high reproducibility and are more robust to the substrate defects.

## A Magnetic Field Compatible Graphene Transmon

Speaker:

Mr James Kroll
From:

QuTech Institute, Delft University of Technology
When:

4pm Thursday 6 April 2017
Where:

CQC2T Conference Room, Level 2 Newton Building, UNSW Hybrid circuit QED is a key tool for readout and scaling of both semiconductor-based spin and topological quantum computing schemes. However, traditional approaches to circuit QED are incompatible with the strong external magnetic fields required for these qubits. We present previous work on superconducting CPW resonators and graphene SNS Josephson junctions that are engineered to survive parallel applied fields up to 6 T. We then combine these elements to realise a magnetic field compatible transmon qubit operating at 1 T.

## Parametric amplification with quantum dots

Speaker:

Dr Matthew House
From:

UNSW CQC2T
When:

4pm Thursday 30 March 2017
Where:

CQC2T Conference Room, Level 2 Newton Building, UNSW At present the sensitivity of spin qubit measurements is not limited by any fundamental physics but, typically, by the noise floor of the first-stage amplifier. In the superconducting qubit community the Josephson Parametric Amplifier (JPA) has been developed to enable fast qubit readout, which has demonstrated quantum-limited noise performance. But the JPA is highly sensitive to magnetic fields and is not ideal for integration with spin qubit experiments. An alternative possibility is to implement a parametric amplifier by taking advantage of the nonlinear capacitance of a quantum dot.

## A Potential Single-Photon Source Driven by a Surface Acoustic Wave

Speaker:

Dr Yousun Chung
From:

UNSW CQC2T
When:

4pm Thursday 23 March 2017
Where:

CQC2T Conference Room, Level 2 Newton Building, UNSW Quantum cryptography requires a high-rate, true single-photon source in order to attain guaranteed security, while photon-based qubits offer the advantage of compatibility with quantum communication frameworks. We have developed a method of creating lateral p-n junctions in undoped GaAs wafers capable of producing single photons using a surface acoustic wave (SAW). In a piezoelectric material, a SAW consists of both an electrostatic potential and an elastic wave travelling parallel to the surface.

## Thermal-error regime in high-accuracy gigahertz single-electron pumping

Speaker:

Mr Ruichen Zhao
From:

UNSW CQC2T
When:

4pm Thursday 16 March 2017
Where:

CQC2T Conference Room, Level 2 Newton Building, UNSW Single-electron pumps based on semiconductor quantum dots are promising candidates for the emerging quantum standard of electrical current. They can transfer discrete charges with part-per-million (ppm) precision in nanosecond time scales. Here, we employ a metal-oxide-semiconductor silicon quantum dot to experimentally demonstrate high-accuracy gigahertz single-electron pumping in the regime where the thermal excitation of electrons, during the equilibrium charge capturing process, is the predominant error mechanism.

## The emergence of chaos in a single nuclear spin of a donor in silicon

Speaker:

Dr Vincent Mourik
From:

CQC2T, UNSW
When:

4pm Thursday 9 March 2017
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW Classical conservative systems usually exhibit rapid dispersion of initial conditions – chaos – while the corresponding quantum equivalent system exhibits quasi-periodicity, localization, and tunneling through classically forbidden regions in phase space. How to reconcile these strikingly different behaviors has been the topic of active theoretical debate, but is accompanied by few experimental results. We propose an experiment aimed at realizing the real-time experimental observation of a single quantum system whose dynamics is classically chaotic – a periodically-driven nonlinear top.

## Imaging a donor-based quantum dot wavefunction in silicon

Speaker:

Dr Benoit Voisin
From:

CQC2T, UNSW
When:

4pm Thursday 2 March 2017
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW Spins in silicon have proven to be a suitable platform for the development quantum technologies. Understanding and controlling spin coupling is now a formidable challenge to overcome. In this talk our most recent results will be reviewed, where atomic scale STM fabrication is combined with low temperature donor imaging to enable local measurements of quantum dots in the STM. This technique will allow manipulation and local read-out of donor states, beneficial from the understanding of qubit coupling in quantum computation to the topological properties of large scale complex arrays of spins.

## Robust exchange interactions in silicon from valley polarization and filtering

Speaker:

Dr Joseph Salfi
From:

CQC2T, UNSW
When:

4pm Thursday 23 February 2017
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW Heisenberg exchange is a key process for entangling single spin qubits and defining logical spin qubits in silicon. However, the role of valley degrees of freedom in exchange is not yet experimentally understood. Here we spatially map the exchange interaction between a single donor atom and a single-electron quantum dot that can be positioned with sub-nm precision using a scanning tunneling microscope. Exchange is found to vary smoothly in space, due to the disorder-free interface for the dot.

## Protocol for the transfer of a quantum state from a photonic qubit to a gate-defi ned quantum dot

Speaker:

Mr Benjamin Joecker
From:

CQC2T, UNSW
When:

4pm Thursday 16 February 2017
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW An interface between a well-functioning, scalable stationary and a photonic qubit could substantially advance quantum communication applications and serve as an interconnect between future quantum processors. Qubits consisting of gate-defi ned quantum dots in GaAs are electrically controllable with high delity, whereas qubits that can realize bound exciton states are established as an optical interface. Here, I present a protocol to transfer the state of a photonic qubit to a gate-defined quantum dot single-spin qubit as well as to a two-spin qubit.

## Majorana Qubits

Speaker:

Professor Leo Kouwenhoven
From:

Microsoft Station Q at Delft and QuTech, Delft University of Technology, The Netherlands
When:

4pm Thursday 12 January 2017
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW Majoranas in semiconductor nanowires can be probed via various electrical measurements. Tunnel spectroscopy have revealed zero-bias peaks in the differential conductance. New observations include quantum superpositions of Majorana states leading, for instance, to a 4pi current phase relation or a fractional Josephson effect. When the existence of Majoranas is firmly established, the next challenge is to build Majorana qubits. We discuss the different qubit schemes and report on our first building blocks.

## On the use of RF probes to sense Quantum Dots

Speaker:

Mr Prasanna Pakkiam
From:

CQC2T, UNSW
When:

4pm Thursday 17 November 2016
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW As quantum dot devices grow in complexity, more groups are adopting the use of RF probes to measure the state of their qubits due to the sensor’s compact real-estate, high measurement bandwidth and general performance under low frequency noise. This seminar is to provide a general overview of the RF probe, specifically in the case of RF reflectometry, as applied to gate-defined and donor-based quantum dot systems. The state of the art, as seen in literature, shall be covered while noting some technical subtleties involved in optimising the sensor.

## Improvement and Optimisation of Electron Spin State Read-Out

Speaker:

Mr Daniel Keith
From:

CQC2T, UNSW
When:

4pm Thursday 10 November 2016
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW High fidelity qubit state readout is one of the essential steps to achieve universal quantum computation. In this talk I will focus on spin state systems and what progress has been made to improve spin read-out over the past ten or so years as well as what further optimisations we have been investigating. Various parameters, such as device architecture and magnetic field strength, can be optimised to produce the highest read-out fidelities possible for a particular system.

## High-precision single-electron current source based on a silicon quantum dot

Speaker:

Dr Tuomo Tanttu
From:

CQC2T, UNSW
When:

4pm Thursday 27 October 2016
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW In addition of being extremely successful platforms for spin qubits, silicon quantum dots can be operated as robust quantized current sources. These current pumps would provide a convenient realization for the emerging quantum SI ampere, which would be based on fixed elementary charge. Here, we study silicon quantum dot charge pump that can output 80 pA current with uncertainty of less than 30 ppm and show that the pumping dot can be manipulated with external electric confinement [1]. Electron counting is performed with nearby integrated charge sensor.

## Performance of a scalable silicon quantum processor

Speaker:

Dr Guilherme Tosi
From:

CQC2T, UNSW
When:

4pm Thursday 20 October 2016
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW We have recently proposed [1] a new scheme to operate and couple Si:P spin qubits that does not require precise donor placement and spaces them apart allowing plenty of room for interconnects. Such a scheme relies on manipulating the electron charge state, and therefore care has to be taken in protecting the qubit from charge noise. In this seminar I will discuss how different sources of noise affect the performance of our quantum gates, and show that, by operating the qubits in regimes where they are protected from noise, fidelities compatible with quantum error correction are within reach.

## Superconducting interference in a one dimensional system

Speaker:

Dr Vincent Mourik
From:

UNSW CQC2T
When:

4 pm Thursday 6 October 2016
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW Semiconducting nanowires coupled to superconductors are crucial in proposals for inducing, detecting and controlling topological superconductivity and Majorana fermion bound states. Using NbTiN-InSb-NbTiN Josephson junctions, we study supercurrents flowing in quasi-ballistic nanowires with strong spin-orbit interaction and in high magnetic fields, thus combining the essential ingredients required for Majorana fermions. Without taking particular care of the chemical potential in the nanowire, we observe supercurrent oscillations at finite magnetic field.

## ESR at the quantum limit using high-Q superconducting resonators

Speaker:

Dr Jarryd Pla
From:

School of Electrical Engineering & Telecommunications UNSW
When:

4 pm Thursday 13 October 2016
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW The detection and characterization of paramagnetic species by electron spin resonance (ESR) spectroscopy has numerous applications in chemistry, biology, and materials science [1]. Most ESR spectrometers rely on the inductive detection of the small microwave signals emitted by the spins during their Larmor precession into a microwave resonator.

## Fabrication of 3-D phononic crystals for thermal transport management

Speaker:

Mr Mykhailo Savytskyi
From:

UNSW School of Electrical Engineering and Telecommunications
When:

4pm Thursday 29 September 2016
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW Thermal transport is an important physical phenomenon, and it has recently become even more relevant for the reduction of energy losses and the increase of efficiency in novel devices based on thermoelectricity [1]. Significant reduction of thermal conduction was recently achieved by coherent modification of phonon modes [2], with the help of periodic phononic crystal structures. However, currently the experimental studies have only been performed for two-dimensional (2-D) nanostructures.

## Overview of Optomechanics in Hamburg: SQL and Beyond

Speaker:

Dr Sacha Kocsis
From:

Hamburg University
When:

2pm Tuesday 27 September 2016
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW Optomechanics deals with the interaction between electromagnetic radiation and mechanical objects. The optomechanical interaction is caused by radiation-pressure force, which was experimentally observed over a century ago. Modern interest in optomechanics is motivated from a few different directions: ultra-sensitive optical detection of forces, displacements and accelerations (e.g.

## Optical cavity for coupling single atom qubits

Speaker:

Dr Bin Bin Xu
From:

UNSW CQC2T
When:

4pm Thursday 22 September 2016
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW We put forward a hybrid approach in which optical cavities are applied to coupling qubits and electronic devices are used to readout. The key point is to guarantee the electronics compatible with photonics. We propose that using doping Phosphorus in silicon to form a conductive layer acting as electrodes and conducting wires in the cavity. The optical cavity could be used to transfer the photons to couple single atom qubits.

## Recent progress on hybrid spin readout of single erbium atoms in silicon

Speaker:

Dr Chunming Yin
From:

UNSW CQC2T
When:

4pm Thursday 8 September 2016
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW Optical addressing provides optical/electrical access to single erbium atoms in silicon. The next step is to look at its nuclear spin dynamics. In this presentation, I’ll show the recent experimental progress with more efficient readout at lower temperature, and an outlook for future work.

## Waveguide coupling of single photons from a solid state emitter

Speaker:

Mr Samuele Grandi
From:

Faculty of Natural Sciences, Department of Physics, Imperial College London
When:

4pm Thursday 15 September 2016
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW The organic dye molecule dibenzoterrylene (DBT) in an anthracene crystal matrix is a promising

candidate for single photon emission. At cryogenic temperatures, this system presents a narrow

lifetime-limited transition at 785nm, with a quantum yield close to unity. Moreover, DBT

molecules have been shown to act as a mediator for photon-photon interactions, by inducing a

phase-shift on a passing photon when another photon is present. These features make DBT

molecules a powerful tool for quantum information purposes, including use as single photon sources

## A Cavity-Enhanced Room-Temperature Broadband Quantum Memory

Speaker:

Mr Dylan Saunders
From:

University of Oxford
When:

1pm Friday 26 August 2016
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW Broadband quantum memories hold great promise as multiplexing elements in future photonic quantum information protocols. Alkali vapour Raman memories combine high-bandwidth storage, on-demand read-out, and operation at room temperature without collisional fluorescence noise. However, previous implementations have required large control pulse energies and suffered from four-wave mixing noise.

## Full and inverse counting statistics of a donor bound electron coupled to a single reservoir

Speaker:

Mr Samuel Gorman
From:

UNSW CQC2T
When:

4pm Thursday 25 August 2016
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW The distribution of tunnel events in a system can reveal a large amount of information about the system dynamics that may not be immediately apparent. The statistics of this distribution can be measured by counting the number of transition events within a certain time: This is known as full counting statistics (FCS). In this talk I will give an overview of full counting statistics and introduce a new technique known as inverse counting statistics (ICS), which can be used to obtain further information about the dynamics of the system.

## A surface code quantum computer architecture using donors in silicon

Speaker:

Mr Sam Hile
From:

UNSW CQC2T
When:

4pm Thursday 11 August 2016
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW Phosphorus donor nuclear spins in silicon have long coherence times and a small spatial footprint, making them an attractive candidate for a large-scale quantum processor. We present an architecture that takes advantage of the uniformity of donors and the resolution of hydrogen desorbtion lithography to implement an error corrected array using the 2D surface code. The difficulties of independent qubit control and tuning/trimming are avoided and the complexity of all quantum operations is distilled to careful loading and unloading of electrons.

## Two-Particle-Three-Qubit GHZ Entanglement and Teleportation in Self-assembled Quantum Dot

Speaker:

Dr Yu He
From:

UNSW CQC2T
When:

4pm Thursday 4 August 2016
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW Self-assembled quantum dot provides us a platform combined with highly indistinguishable single photon source and well defined spin qubit. In this talk, I will present the first experiment on generating Two-Particle-Three-Qubit type GHZ entanglement in this system. Based on this entanglement state, a photon state is teleportated to a spin of a quantum dot in 5 meters distance.

## Preliminary works towards the acceptor spin cavity QED

Speaker:

Dr Takashi Kobayashi
From:

UNSW CQC2T
When:

4pm Thursday 28 July 2016
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW The acceptor spin is predicted to have a large electric dipole moment and a long coherence time in the well-controlled strain and electric field. These features are suitable for realization of spin qubits wired-up by a superconducting cavity. In this talk, I will present some preliminary works to evaluate the coherence time of acceptors and incorporate the electric field and strain with a high-Q cavity.

## Photonic Structure Coupling and Strain Sensing with Single Photon Emitters in Diamond

Speaker:

Sebastian Knauer
From:

University of Bristol
When:

4pm Tuesday 5th July 2016
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW The interaction of photonic structures with single photon emitters at visible wavelengths is of great interest in fundamental quantum information processing and biological sensing. At room temperature, colour centres in diamond have shown great advantages over other solid state emitters in many experiments.

## Supressing Segregation in Highly Doped Silicon Monolayers

Speaker:

Dr Joris Keizer
From:

UNSW CQC2T
When:

4pm Thursday 30th June 2016
Where:

CQC2T Conference Room Level 2, Newton Building, UNSW Abrupt dopant profiles and low resistivity are highly sought after qualities in the silicon microelectronics industry and, more recently, in the development of an all epitaxial Si:P based quantum computer. Previously, we have shown that increasing the dopant density by growing multiple layers is ultimately limited the formation of P-P dimers due to the segregation of dopants between multi-layers [1].

## Validation of an accurate Si single electron pump with traceability to primary standards

Speaker:

Mr Ruichen Zhao
From:

UNSW CQC2T
When:

4pm Thursday 23rd June 2016
Where:

CQC2T Conference Room, Level 2 Newton Building, UNSW ## Strain Mapping in Silicon Nanotransistors

Speaker:

Mr Guangchong Hu
From:

CQC2T at UNSW
When:

4pm Thursday 9 June 2016
Where:

CQC2T Conference Room, Lev 2 Newton Building, UNSW ## Optical absorption and the creation of excitons in FinFETs

Speaker:

Mr Gabriele de Boo
From:

CQC2T at UNSW
When:

4pm Thursday 2nd June 2016
Where:

CQC2T conference room, Lev 2 Newton Building, UNSW ## Spin dynamics of acceptor atoms in silicon

Speaker:

Mr Joost van der Heijden
From:

CQC2T at UNSW
When:

4pm Thursday 26th May 2016
Where:

CQC2T Conference Room, Lev 2 Newton Building, UNSW ## Effect of Valleys and Parasitic Spin on a Quantum Dot Qubit

Speaker:

Dr Henry Yang
From:

CQC2T at UNSW
When:

4pm Thursday 19th May 2016
Where:

CQC2T Conference Room, Lev 2 Newton Building, UNSW ## Two talks: Pulse tube noise – effect on the qubit/ Improving electron spin initialisation fidelities by digital feedback

Speaker:

Dr Arne Laucht and Mr Mark Johnson
From:

CQC2T at UNSW
When:

4pm Thursday 12 May 2016
Where:

CQC2T Conference Room, Level 2 Newton Building, UNSW ## Exchange coupling in a three-qubit system based on silicon quantum dots

Speaker:

Dr Kok Wai Chan
From:

CQC2T UNSW
When:

Note new time: 3-4pm Friday 6th May 2016
Where:

CQC2T Conference Room, Lev 2 Newton Bldg, UNSW ## Invitation: Schrӧdinger's Bird (the Art of Quantum Physics)

Speaker:

Artist: Steve Burbach
From:

24th May to 12th June 11am - 5 pm daily
When:

OPENING NIGHT: Wed 25th May 6-8pm (opened by Prof. Sven Rogge; Program Director CQC2T)
Where:

The Bondi Pavilion Gallery, Queen Elizabeth Drive, Bondi Beach, 2026 I would love you to join me at the opening of my latest exhibition, Schrӧdinger's Bird, which represents a unique art and science collaboration with the world renowned ARC Centre of Excellence for Quantum Computation and Communication Technology (CQC2T). The exhibition encompasses a collection of drawings, paintings, animation and machinery that explores the heart of Quantum Physics and the new science of quantum computation which is the area of focus of this world-leading research group.

When: The exhibition runs from the 24th May to 12th June 11am - 5 pm daily;

## A silicon-based surface code quantum computer and reducing the overhead of magic state distillation.

Speaker:

Mr Joe O’Gorman
From:

Materials Department, Oxford University
When:

4pm Thursday 28 April 2016
Where:

CQC2T Lev 2 Conference Room, Newton Buidling, UNSW Since the Kane proposal our understanding of the need for and methods of quantum error correction has developed significantly - motivating improved architectures for quantum computing, in particular based on the surface code. I’ll present an analysis of a novel scheme for implementing a surface code with donor spins in silicon using their dipolar interaction and a repeating mechanical motion.

## Taking Hydrogen Resist Lithography to the Third Dimension

Speaker:

Dr Matthias Koch
From:

CQC2T UNSW
When:

4pm Thursday 21 April 2016
Where:

CQC2T conference Room, Level 2 Newton Building UNSW Hydrogen-resist lithography on Si(100) has become a reliable tool to fabricate nano-scale circuits. Traditionally, our devices were constricted to a single 2D plane. Our technique can be adapted to the fabrication in 3D as well. In this talk I will discuss the requirements on alignment and surface quality. Finally, I will present results of two working 3D single electron transistors, one with a top gate and one with an additional single donor tuned by the top gate.

## Experimental tests of quantum reality

Speaker:

Dr George Knee
From:

Department of Materials, Oxford University
When:

3pm Friday 22nd April 2016
Where:

CQC2T Lev 2 Conference Room, Newton Building, UNSW Quantum mechanics is often said to be a ‘strange’ theory: but what exactly is meant by this? Often, what is meant is the failure of our ability to apply certain classical notions to the atomic or molecular scale. I will discuss two such notions of classicality, i) the idea that objects have definite properties independent of measurement and ii) that uncertainty can be thought of as merely imperfect knowledge.

## Temporal Quantum Interference: A Many-Worlds Approach

Speaker:

Mr Solomon Freer
From:

CQC2T at UNSW
When:

4pm Thursday 14 April 2016
Where:

CQC2T Level 2 Conference Room, Newton Building, UNSW Measurement of a quantum system appears to create a discontinuity in its evolution, since superpositions are collapsed into eigenstates.

The Many World Interpretation (MWI) posits that this collapse is merely subjective, providing a new perspective on the apparent paradoxes invoked by incompatible measurements of the same quantum system. Solomon will discuss this approach and present results for a violation of a "Bell's inequality in time": the Leggett-Garg inequality.

## Development of WSi superconducting single photon detectors

Speaker:

Dr Shouyi Xie
From:

CQC2T at UNSW
When:

4pm Thursday 7th April 2016
Where:

CQC2T, Level 2 Newton Building UNSW ## Exploring frequency re-use in circuit QED using selective broadcasting

Speaker:

Mr Serwan Asaad
From:

CQC2T UNSW
When:

4pm Thursday 31st March 2016
Where:

CQC2T conference room Level 2 Newton Building, UNSW ## Imaging and controlling interacting donor wave functions in Silicon

Speaker:

Dr Juanita Bocquel
From:

CQC2T
When:

4pm Thursday 24 March 2016
Where:

Lev 2, Newton Building, CQC2T, UNSW ## High sensitivity RF measurement techniques for scalable atomic precision devices

Speaker:

Dr Matthew House
From:

CQC2T, UNSW
When:

4pm Thursday 17th March 2016
Where:

Lev 2 Conference Room, CQC2T, Newton Building, UNSW ## A valley driven spin qubit

Speaker:

Mr Wister Huang
From:

UNSW, CQC2T
When:

4pm Thursday 10 March 2016
Where:

Level 2 CQC2T conference room, Newton Building, UNSW ## Magnetic Molecules on surfaces: from magnetic bistability towards quantum coherence at the single molecule level

Speaker:

Professor Roberta Sessoli
From:

Department of Chemistry, University of Florence (Italy)
When:

Wednesday 9th March 2016 at 3pm
Where:

CQC2T Level 2 Conference Room UNSW Abstract: Magnetic molecules with magnetic bistability have represented the ideal workbench for the investigation of quantum effects in the magnetization dynamics and are now studied at the single molecule level thanks to scanning probe techniques and synchrotron experiments. Though magnetic hysteresis has been observed on isolated molecules on surface and even enhanced by the interaction with the substrate, cryogenic temperatures are necessary to preserve the magnetic information.

## Transport characteristics of coupled quantum dots prepared on SOI

Speaker:

Prof Shunro Oda
From:

Quantum Nanoelectronics Research Center, Tokyo Institute of Technology
When:

12pm Friday 4 March 2016
Where:

Centre for Quantum Computation & Communication Technology, Level 2 Newton Building, Conference Room Abstract: Recent progress in qubit operation in isotropically enriched 28Si quantum dots attracted attention since it solved problem of decoherence of qubits. A major remaining issue for practical qubit application is integration technology for multiple qubits. MOS structure is promising for large scale integration.

## Coherent control and detection of orbital superpositions in silicon donor impurities

Speaker:

Professor Ben Murdin
From:

Advanced Technology Institute, University of Surrey
When:

4pm, Thursday, 3rd March 2016
Where:

CQC2T Conference Room, Level 2 Newton Building, UNSW Abstract: Shallow donor impurities in silicon, once frozen out at low temperature, share many properties in common with free hydrogen atoms [1]. They have long been the subject of spectroscopic investigation, but it is only very recently [2,3] that it has been possible to investigate the time-domain dynamics of orbital excitations such as the 1s to 2p, due to the difficulty of obtaining short, intense pulses in the relevant wavelength range, around 10THz.

## Spin-Orbit Torques

Speaker:

Prof Allan Macdonald
From:

The University of Texas
When:

4pm Thursday 25th February 2016
Where:

Centre for Quantum Computation & Communication Technology, Level 2 Newton Building, Conference Room Abstract: A series of fundamental discoveries over the past thirty years has dramatically improved our ability to read, write, and process magnetically stored information. I will briefly review some of these advances before focusing on the recently discovered spin-orbit torques, which act on the collective spin of thin film ferromagnets when they are placed on a substrate with strong spin-orbit interactions and are particularly promising for applications.

## Silicon Quantum Processor with Robust Long-Distance Qubit Couplings

Speaker:

Dr Guilherme Tosi
From:

University of New South Wales, Australia
When:

4pm Thursday 5 November 2015
Where:

Centre for Quantum Computation and Communication Technology, Level 2 Newton Building, Conference Room Guilherme will present a scalable design for a silicon quantum processor that exploits the electric dipole induced on a donor with a top-gated structure. Quantum information is encoded in either the nuclear-spin or the flip-flop states of electron and nucleus. The physical qubits are spaced by hundreds of nanometers and coupled through direct electric dipole interactions and/or photonic links. They can be controlled at high-speeds by extremely low-power microwave fields, while still preserving their outstanding coherence times.

## Design, Fabrication and Test of a Four Superconducting Quantum-Bit Processor

Speaker:

Dr Vivien Schmitt
From:

University of New South Wales, Australia
When:

4pm Thursday 29 October 2015
Where:

Conference Room, 2nd Floor Newton Building, CQC2T ## A Dressed Spin Qubit in Silicon

Speaker:

Dr Arne Laucht
From:

University of New South Wales, Australia
When:

4pm Thursday 22 October 2015
Where:

Conference Room, 2nd Floor Newton Building, CQC2T ## The quantum properties of magnetic atoms on surfaces

Speaker:

Dr Andreas Heinrich
From:

IBM Research, USA
When:

4:30pm Tuesday 13 October 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW The scanning tunneling microscope is an amazing experimental tool because of its atomic-scale spatial resolution.

This can be combined with the use of low temperatures, culminating in precise atom manipulation and spectroscopy with microvolt energy resolution. In this talk I will apply these techniques to the investigation of the quantum spin properties of transition metal atoms on surfaces. We will conclude with our recent measurements of electron spin resonance in an STM on individual Fe atoms supported on an insulating thin film.

## Experimental loophole-free violation of a Bell inequality using entangled electron spins separated by 1.3 km

Speaker:

Dr Bas Hensen
From:

QuTech, Kavli Institute of Nanoscience, Delft University of Technology, Netherlands
When:

4pm Thursday 8 October 2015
Where:

School of Physics, Room 64 In his seminal work^{[1]}, John Bell proved that no theory of nature that obeys locality, realism and free will can reproduce all the predictions of quantum theory. In the past decades, numerous ingenious Bell inequality tests have been reported. However, because of experimental limitations, all experiments to date required additional assumptions to obtain a contradiction with local realism, resulting in loopholes.

## Towards efficient optical/electrical readout of a single nuclear spin in a silicon nano-transistor

Speaker:

Dr Chunming Yin
From:

University of New South Wales
When:

4pm Thursday 24 September 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW ## Single-Electron Pumps Investigated by Precision DC Measurements and Counting

Speaker:

Dr Lukas Fricke
From:

University of New South Wales
When:

4pm Thursday 17 September 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW ## Ultrafast Dynamics of Photoexcited Insulators Probed by Time- and Angle-Resolved Photoemission

Speaker:

Prof Martin Wolf
From:

Fritz-Haber-Institute of the Max Planck Society, Germany
When:

4pm Friday 4 September 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW Photoexcitation above the band gap of insulators or semiconductors may lead to non-equilibrium processes on ultrafast timescales. Depending on excitation density their dynamics are governed by exciton formation and electron-phonon scattering or more complex phenomena leading to phase transitions. These processes typically occur on ultrafast (femto- to picosecond) time scales. We employ femtosecond time- and angle-resolved photoemission spectroscopy (trARPES) to study surface excition formation as well as ultrafast insulator-to-metal (IM) transitions in several materials.

## The art of science of art of science of..

Speaker:

Mr Steve Durbach
From:

Sid Sledge
When:

4pm Thursday 3 September 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW I am an artist with a background in science. The art I make is inspired by scientific theories and thinking, and engaging with scientists across different fields and exploring their ideas is a key catalyst for my work. Having had the pleasure of meeting and talking with several members of this group, I got a sense of the extraordinary work being done here.

## Reflectometry observation of inter-donor coupling & preliminary work towards the acceptor spin cavity QED

Speaker:

Dr Takashi Kobayashi
From:

University of New South Wales
When:

4pm Thursday 27 August 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW ## Dispersive readout of Si-MOS double quantum dots

Speaker:

Dr Henry Yang
From:

University of New South Wales
When:

4pm Thursday 25 June 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW ## In-situ Electrostatic Control of Donor Structures in STM

Speaker:

Dr Benoit Voisin
From:

University of New South Wales
When:

4pm Thursday 18 June 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW ## Charge Detection for a Silicon Single-Electron Pump

Speaker:

Ms Yuxin Sun
From:

University of New South Wales
When:

4pm Thursday 11 June 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW ## Spectroscopy of the Crystal Field Levels of Single Erbium Atoms in Silicon

Speaker:

Mr Gabriele de Boo
From:

University of New South Wales
When:

4pm Thursday 4 June 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW ## High-Fidelity Rapid Readout of an Electron Spin via the Single Donor D- Charge State

Speaker:

Mr Thomas Watson
From:

University of New South Wales, Australia
When:

4pm Thursday 28 May 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW ## Investigation and Manipulation of Single Magnetic Skyrmions

Speaker:

Dr Niklas Romming
From:

University of Hamburg, Germany
When:

4pm Tuesday 26 May 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW Magnetism in thin films can significantly deviate from commonly known magnetic configurations in bulk systems due to low dimensionality, hybridization effects, a change of the lattice constant, stacking and broken inversion symmetry at interfaces. This can lead to non-collinear spin states such as spin spirals or skyrmions. Especially skyrmions offer great potential as information carriers in future robust, high-density, and energy-efficient spintronic devices.

## Designing Silicon Quantum Computer Devices with Classical & Quantum Techniques

Speaker:

Dr Fahd Mohiyaddin
From:

University of New South Wales
When:

4pm Thursday 14 May 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW ## Spin-Orbit Coupling and Operation of Multi-Valley Spin Qubits

Speaker:

Dr Menno Veldhorst
From:

University of New South Wales
When:

4pm Thursday 7 May 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW ## Charge Sensing of a Si:P Triple Dot and Determining Interdot Tunnel Couplings

Speaker:

Dr Matthew Broome
From:

University of New South Wales
When:

4pm Thursday 23 April 2015
Where:

Thursday 23 April 2015 ## Single-molecule electron spin resonance spectroscopy under ambient conditions

Speaker:

Mr Qi Zhang
From:

University of New South Wales
When:

4pm Thursday 16 April 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW Magnetic resonance is essential in revealing the structure and dynamics of biomolecules. However, measuring the magnetic resonance spectrum of single biomolecules has remained an elusive goal. In this talk, I will introduce our recent results of detecting the electron spin resonance signal from a single spin-labeled protein under ambient conditions. As a sensor, we use a single nitrogen vacancy center in bulk diamond in close proximity to the protein. Some explorations of scallable quantum computation with this technique will also be demonstrated.

## Silicon based quantum dot hybrid qubits

Speaker:

Dr Dohun Kim
From:

Yonsei University, Korea
When:

11am Tuesday 14 April 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW The charge and spin degrees of freedom of an electron constitute natural bases for constructing quantum two level systems, or qubits, in semiconductor quantum dots. The quantum dot charge qubit offers a simple architecture and high-speed operation, but generally suffers from fast dephasing due to strong coupling of the environment to the electron’s charge. On the other hand, quantum dot spin qubits have demonstrated long coherence times, but their manipulation is often slower than desired for important future applications.

## Charge and spin measurement strategies for the next generation of atomic precision devices

Speaker:

Dr Matthew House
From:

University of New South Wales
When:

4pm Thursday 26 March 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW ## Towards the Quantum Ampere using Silicon Single-Electron Pumps

Speaker:

Dr Alessandro Rossi
From:

University of New South Wales
When:

4pm Thursday 19 March 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW ## Device Fabrication and Experimental Outlook for Si-MOS Multi-Quantum Dots

Speaker:

Mr Jason Hwang
From:

University of New South Wales
When:

4pm Thursday 12 March 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW ## Tuning Electrical and Optical properties of Nanopore Sensors

Speaker:

Mr Daniel Bar
From:

University of New South Wales
When:

4pm Thursday 5 March 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW ## A model of the single atom electron pump

Speaker:

Mr Joost van der Heijden
From:

University of New South Wales
When:

4pm Thursday 26 February 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW ## Designs for integrated quantum information devices and systems

Speaker:

Prof Kae Nemoto
From:

National Institute of Informatics, Japan
When:

4pm Monday 23 February 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW There have been many architectures for quantum computer and quantum information devices proposed, yet we face a gap between these proof-of-principle idea and feasible quantum devices. We focus on an integrated cavity device based on a single diamond NV center to identify the problems and obstacles integrating necessary elements to perform certain tasks within a threshold error.

## Narrowing of the Overhauser field distribution in a GaAs double quantum dot

Speaker:

Ms Stefanie Tenberg
From:

University of New South Wales
When:

4pm Thursday 12 February 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW For GaAs spin qubits all essential operations for QI have been demonstrated and coherence times are increasing. However, coherent control is still, like in many other electron spin qubit systems, impaired by the fluctuating nuclear spin bath of the host material. Previous experiments have shown dynamic nuclear polarization with feedback to significantly prolong de inhomogeneous dephasing time T2∗ by narrowing the distribution of nuclear Overhauser field fluctuations.

## Towards spatially resolved multi-donor structures spectroscopy

Speaker:

Dr Juanita Bocquel
From:

University of New South Wales
When:

4pm Thursday 5 February 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW ## Process Tomography of a Silicon Quantum Memory

Speaker:

Mr Solomon Freer
From:

University of New South Wales
When:

4pm Thursday 29 January 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW Long coherence times and fast manipulation are two desirable qualities of a qubit that for many systems are mutually incompatible. Storing quantum information in an ancillary qubit, i.e. a `quantum memory', is a strategy to address this issue. It is a advantageous property of donor impurities in silicon to have qubits of both qualities in a single lattice site. This talk will present results of the storage and retrieval of quantum information from a single donor electron spin to its host phosphorus nucleus in isotopically-enriched $^{28}$Si.

## Isotope engineering of silicon and diamond for quantum information processing

Speaker:

Prof Kohei M. Itoh
From:

Keio University, Japan
When:

4pm Monday 27 January 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW Key roles of isotope engineering in silicon and diamond quantum information processing are discussed. While removal of the background ^{29}Si nuclear spins is proven crucial for extending the coherence time of spin qubits in silicon, removal of the background ^{28}Si, ^{29}Si, and ^{30}Si mass fluctuations is also shown to be important for defining the nuclear magnetic resonance frequencies of donors such as ^{31}P in silicon. Effects of removing ^{13}C nuclear spins in diamond are also similar.

## Spin qubits in GaAs and Si quantum dots – latest results and directions

Speaker:

Prof Lieven Vandersypen
From:

Kavli Institute of NanoScience, TU Delft, Netherlands
When:

4pm Thursday 22 January 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW ## Compressed Sensing for Quantum State Tomography and Hamiltonian Determination

Speaker:

Dr Kenneth Rudinger
From:

Sandia National Laboratories, USA
When:

2pm Monday 19 January 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW Compressed sensing techniques have been successfully applied to quantum state tomography, enabling the efficient determination of states that are nearly pure, i.e, of low rank. We show how compressed sensing may be used even when the states to be reconstructed are full rank. Instead, the necessary requirement is that the states be sparse in some known basis (e.g. the Pauli basis). Physical systems at high temperatures in thermal equilibrium are important examples of such states.

## Photon-mediated interactions between artificial atoms with waveguide QED

Speaker:

Prof Alexandre Blais
From:

Université de Sherbrooke, Canada
When:

4pm Thursday 15 January 2015
Where:

Conference Room, 2nd Floor Newton Building, UNSW Since the first observation, almost 15 years ago, of coherent oscillations in a superconducting qubit there have been significant developments in the field of superconducting quantum circuits. With improvements of coherence times by over 5 order of magnitude, it is now possible to implement simple quantum algorithms with these circuits. In parallel to these developments, much effort has been invested in using superconducting qubits as artificial atoms to explore quantum optics in unconventional parameter regimes.

## 2018 CQC2T Seminar List

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Date |
Presenter |

Thursday 15 February 2018 | Tim Botzem |

Thursday 22 February 2018 | Joseph Salfi |

Thursday 1 March 2018 | Benoit Voisin |

Thursday 8 March 2018 | Serwan Asaad |

Thursday 15 March 2018 | Sacha Kocsis |

Thursday 22 March 2018 | Chunming Yin |

Thursday 29 March 2018 | No Seminar |

Thursday 5 April 2018 | Matthew House |

Thursday 12 April 2018 | Wister Huang |

Thursday 19 April 2018 | Mitchell Kiczynski |

Thursday 26 April 2018 | Rostyslav Savytskyy |

Thursday 3 May 2018 | Gabriele de Boo |

Thursday 10 May 2018 | Prof Susan Coppersmith |

Thursday 17 May 2018 | Henry Yang |

Thursday 24 May 2018 | No seminar - Science Faculty Dean's Awards |

Thursday 31 May 2018 | Felix Krauth |

Thursday 7 June 2018 | Vivien Schmitt |

Thursday 14 June 2018 | Guangchong Hu |

Thursday 21 June 2018 | Andrey Timofeev |

Thursday 28 June 2018 | Anderson West |

Thursday 5 July 2018 | Matthew Donnelly |

Thursday 12 July 2018 | Mark Johnson |

Thursday 19 July 2018 | Bas Hensen |

Thursday 26 July 2018 | Benjamin Joecker |

Thursday 2 August 2018 | Misha Saiful |

Thursday 9 August 2018 | Yu He |

Thursday 16 August 2018 | Daniel Keith |

Thursday 23 August 2018 | Georgina Carson |

Thursday 30 August 2018 | Rainer Stoehr |

Thursday 6 September 2018 | Emma Cottenham |

Thursday 13 September 2018 | Yousun Chung |

Thursday 20 September 2018 | Ludwik Kranz |

Thursday 27 September 2018 | Ross Leon |

Thursday 4 October 2018 | Mateusz Madzik |

Thursday 11 October 2018 | Michael Jones |

Thursday 18 October 2018 | Tuomo Tanttu |

Thursday 25 October 2018 | Sebastian Knauer |

Thursday 1 November 2018 | Vikas Sewaati |

Thursday 8 November 2018 | Prasanna Pakkiam |

Thursday 15 November 2018 | No seminar - Silicon Quantum Workshop 13-15 November 18 |

Thursday 22 November 2018 | No seminar |

Thursday 29 November 2018 | Vincent Mourik |

Thursday 6 December 2018 | Mark Hogg |