Towards a microwave quantum memory based on an ensemble of electron spins

Quantum memory as a solid-state storage medium is an important ingredient in quantum computing. In the optical domain [1], it underpins applications such as quantum repeaters to achieve long-distance communication. Quantum memories suitable for interfacing with superconducting quantum processors must operate in the microwave regime, which requires operation at millikelvin temperatures in a dilution refrigerator. Such devices could be used to operate a quantum Turing machine architecture with high internal connectivity and built-in long-term memory, thus avoiding overheads from quantum error correction [2, 3]. Specific memory elements can also allow microwave to optical conversion [4], enabling an interface between distant quantum processors.
In this talk, I will outline the prospects and challenges of implementing a quantum memory based on electron spins. In particular, I will present my ongoing research at NPL about controlling microwave emission from a spin ensemble which is a requirement for random access of writing to and reading from the register. We demonstrate such ability by using a resonator whose frequency can be rapidly tuned with a bias current. We store excitations in an ensemble of rare-earth-ion and suppress on-demand the echo emission (`echo silencing') by two methods: 1) detuning the resonator during the spin rephasing, and 2) subjecting spins to magnetic field gradients due to the bias current itself. We also show that spin coherence is preserved during silencing.
During the talk, I will also discuss my vision for future research, elucidating laboratory start up plan and illustrate possible links for strengthening the current research themes pursued in the condensed matter physics department.
									
[1] Lvovsky, et al., Nat. Photonics 3, 706 (2009).
[2] P. Rabl et al., Phys. Rev. Lett. 97, 033003 (2006).
[3] K. Tordrup et al., Phys. Rev. Lett. 101, 040501 (2008)
[4] E. Saglamyurek et al., Nature Photonics 9, 83 (2015)