(image by Gavin Morley)
I have recently started a PhD at the University of Warwick under the supervision of Dr Gavin Morley, after graduating with a Master's degree in Physics (MPhys) from the University of Bath. During my PhD, I will investigate electrically detected magnetic resonance (EDMR) in phosphorous- and bismuth-doped silicon, for applications in quantum information processing (QIP).
Since Kane's seminal paper proposing a silicon-based quantum computer, electron and nuclear spins of dopants in silicon have been studied for QIP due to their relatively long coherence times . This is due to the relatively few nuclear spins in natural abundance silicon, as well as the low spin-orbit coupling . Coherence times can be improved further by using isotopically purified 28Si , .
In an external magnetic field, the spin up and spin down states of electrons of paramagnetic species becomes split in energy. Spin qubits can be manipulated by pulsed electron paramagnetic resonance (EPR) . In order to build a working quantum computer, one must also be able to read out the states of qubits in the system. The electronic spin state of a donor atom represents a qubit (shown by the blue arrows in the image above) and can affect the mobility of nearby conduction band electrons in a sample (shown by the green arrows). The conduction band electrons are spin-polarised by the large magnetic field and can become momentarily trapped by a donor atom if their spin is anti-parallel to that of the qubit. This is one effect which has been used to perform EDMR and has previously been demonstrated in doped silicon samples .
The high magnetic fields (14.1T) and high frequency light source (396.8GHz) available in Warwick provide a unique opportunity to investigate this system for QIP since the high magnetic fields and low temperatures available make it possible to initialise the system in a very pure quantum state. We are currently in the process of designing a suitable probe for the spectrometer which will also make it possible to manipulate the nuclear spins simultaneously, and thus conduct electron-nuclear double resonance (ENDOR) experiments. This will give us full access to the 20-dimensional Hilbert space of bismuth dopants (electron spin 1/2 and nuclear spin 9/2), and potentially allow us to study novel quantum error-correction schemes.
 B E Kane, A silicon-based nuclear spin quantum computer, Nature 393 133-137 (1998)
 A M Tyryshkin, S A Lyon, A V Astashkin and A M Raitsimring, Electron spin relaxation times of phosphorous donors in silicon, Phys. Rev. B 68 193207 (2003)
 A M Tyryshkin, S Tojo, J J L Morton, H Riemann, N V Abrosimov, P Becker, H-J Pohl, T Schenkel, M L W Thewalt, K M Itoh and S A Lyon, Electron spin coherence exceeding seconds in high-purity silicon, Nature Mat. 11 143-147 (2012)
 M Steger, K Saeedi, M L W Thewalt, J J L Morton, H Riemann, N V Abrosimov, P Becker and H-J Pohl, Quantum information storage for over 180s using donor spins in a 28Si “semiconductor vacuum”, Science 336 1280-1283 (2012)
 A Schweiger and G Jeschke, Principles of pulsed electron paramagnetic resonances (Oxford: Oxford University Press, 2001)
 G W Morley, D R McCamey, H A Seipel, L-C Brunel, J van Tol and C Boehme, Long-lived spin coherence in silicon with an electrical spin trap readout, Phys. Rev. Lett. 101 207602 (2008)
F16 Milburn House
University of Warwick
a dot p dot tcholakov at warwick dot ac dot uk
+44 24761 50813
My appreciation for music spans many genres and I love going to live gigs. I pursue a keen interest in technology and am fascinated by the complexity of business in a field where the pace of innovation is so rapid. I have also recently taken up and am thoroghly enjoying Tai Chi at the University of Warwick.