Novel emitters and characterisation tools for spin-based quantum technology

Single spins are an excellent platform for the implementation of quantum memories/repeaters for secure quantum networks and nanoscale quantum sensors. In this talk, I will discuss two aspects of my doctoral research work in the field of quantum spintronics.

In the first half of my talk [1], I will describe our effort to develop "smart" spin-based quantum sensors that self-optimise themselves to operate in the regime of maximum sensitivity. I will present an adaptive approach, based on Bayesian estimation, to estimate the key decoherence timescales (T1, T2*and T2) and the corresponding decay exponent for a single qubit, using information gained in preceding experiments. This approach reduces the time required to reach a given uncertainty by a factor up to an order of magnitude, depending on the specific experiment, compared to curve fitting data taken on a pre-determined parameter range. The procedure is not limited to single spins and can be easily adapted to any qubit.

In the second part of my talk [2], I will describe our work on single vanadium centres in SiC, which have recently attracted attention due to direct telecom-wavelength (O-band) emission and the availability of a coherent electron spin. I will report the first observation of spin-dependent optical transitions, a key requirement for spin-photon interfaces. Additionally, by engineering the isotopic composition of the SiC matrix, I will show that we reduce the inhomogeneous spectral distribution of different emitters down to 100 MHz, significantly smaller than any other single quantum emitter. This is very important as the implementation of quantum networks requires all spin-photon interfaces to operate at exactly the same frequency. These results bolster the prospects for single vanadium emitters in SiC as material nodes in scalable telecom quantum networks.

[1] Online adaptive estimation of decoherence timescales for a single qubit
[2] Ultra-narrow inhomogeneous spectral distribution of telecom-wavelength vanadium centres in isotopically-enriched silicon carbide