Coherent control and detection of orbital superpositions in silicon donor impurities

Professor Ben Murdin
Advanced Technology Institute, University of Surrey
4pm, Thursday, 3rd March 2016
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. These new techniques make shallow donors (and also acceptors [4]) attractive for studying atomic physics effects, and for applications in quantum information.

We have measured the population dynamics of electrons orbiting around phosphorus impurities in commercially-available silicon, using a free electron laser as the THz source, and shown that the lattice relaxation lifetime is about 200ps, only 1
order of magnitude shorter than the radiative lifetime of free hydrogen. We have also shown that silicon donor electrons can be put into a coherent superposition of orbital states that lasts for nearly as long as the lattice relaxation time [3,5]. The result of sequences of coherent control pulses can even be read out simply using a voltmeter.

[1] BN Murdin et al Nature Communications 4, 1469 (2013)
[2] NQ Vinh et al, Proc Nat Acad Sci USA 105, 10649 (2008)
[3] PT Greenland et al Nature 465, 1057 (2010).
[4] NQ Vinh et al Phys Rev X 3, 011019 (2013).
[5] KL Litvienenko et al Nat Comm 6, 6549 (2015).

Research Interests
Prof Murdin is an experimentalist interested in the study of electronic and optical properties of semiconductors and semiconductor nanostructures using high-pressures, magnetic-fields, and linear, nonlinear and time resolved infrared spectroscopy. He is a regular user of the Free-Electron Laser, FELIX, in Holland, and is the coordinator and spokesperson for UK Condensed Matter Physics users there. He is also a Programme Advisory Committee member for the Dresden laser, FELBE.

Research Collaborations
Prof Murdin has strong research links with the groups of Prof. Carl Pidgeon at Heriot-Watt University, Prof Gabriel Aeppli at UCL, Prof. Wolfgang Heiss at Uni. Linz, Dr Lesley Cohen at Imperial College London, Dr Tony Krier at Lancaster, Dr Tim Ashley at QinetiQ Ltd and Dr Lex van der Meer at the Free Electron Laser in Utrecht.