Nitrogen-vacancy (NV-) centres in diamond
We work on NV- centres as part of the Oxford-led quantum technology Hub, NQIT (Networked Quantum Information Technology), and as part of the Diamond Science and Technology (DST) Centre for Doctoral Training (CDT).
Bismuth qubits in silicon
The spins of phosphorus atoms in silicon are known to be excellent quantum bits. We have shown that bismuth atoms have similarly advantageous properties including long electron spin coherence times. Our experiments in low magnetic fields highlight the unique features of bismuth qubits.
- GW Morley et al., The initialization and manipulation of quantum information stored in silicon by bismuth dopants, Nature Materials 9, 725 (2010)
- MH Mohammady, GW Morley & TS Monteiro, Bismuth qubits in silicon: The role of EPR cancellation resonances, Physical Review Letters 105, 067602 (2010)
- GW Morley et al., Quantum control of hybrid nuclear-electronic qubits, Nature Materials 12, 103 (2013) with News & Views by Zhao and Wrachtrup. You can even watch our YouTube video discussing this paper or read our press release.
The animation above illustrates fast control of hybrid quantum bits in silicon. We can control the state of an electron spin qubit (blue arrow) quickly with microwaves using magnetic resonance. We can also control the nucleus (red arrow), but this is much slower. In our new experiments we hybridize the electron and the nucleus, allowing us to speed up our control of the combined system by orders of magnitude. Reducing the magnetic field that we apply is enough to hybridize the electronic and nuclear qubits. Animation by GW Morley.
The image above (made by Manuel Voegtli, LCN) shows a bismuth atom in one slice of a silicon crystal. The large light green cloud indicates the likely positions of the bound electron, and the purple arrow is its spin. The bismuth nuclear spin (blue arrow) can tilt in ten different directions, shown in red and yellow.
Electrically-detected pulsed EPR of phosphorous qubits in silicon
We demonstrated a way to make the electrically-detected quantum lifetime of electron spins more than 50 times longer than the previous record. This required the use of a magnetic field 25 times higher than the previous maximum for these experiments.
- GW Morley et al., Long-lived spin coherence in silicon with an electrical spin trap readout, Physical Review Letters 101, 207602 (2008)
Highlighted in Scientific American
- DR McCamey, C Boehme, J van Tol & GW Morley, Method for the generation of nuclear hyperantipolarization in solids without the use of very high magnetic fields of magnetic resonant excitation, Worldwide patent number WO/2009/155563 (2009)
- DR McCamey, J van Tol, GW Morley & C Boehme, Electronic spin storage in an electrically readable nuclear spin memory with a lifetime >100 seconds, Science 330, 1652 (2010)
Our electrically-detected qubit readout experiments use the spin trap mechanism illustrated in the animation above. Electrons (green arrows) flow through a silicon chip and can be trapped by a phosphorus atom with a different electron spin (blue arrow). We also used this technique to electrically read out the nuclear spin (red arrow).
The photo above shows Gavin Morley making devices with nanoscale gold wires for pulsed electrically-detected EPR experiments.