Quantum control of hybrid nuclear-electronic qubits

TL;DR

This paper demonstrates the first quantum control of hybrid nuclear-electronic qubits in bismuth-doped silicon, achieving ultra-fast manipulation and long coherence times, with potential benefits for quantum computing speed.

Contribution

It introduces and experimentally demonstrates quantum control of hybrid nuclear-electronic qubits, a novel regime with faster operations and longer coherence times than previous pure nuclear spin approaches.

Findings

Quantum control achieved in 32 ns, much faster than previous methods.

Coherence times reach 4 ms, five orders of magnitude longer.

Experimental results align with analytical theory without free parameters.

Abstract

Pulsed magnetic resonance is a wide-reaching technology allowing the quantum state of electronic and nuclear spins to be controlled on the timescale of nanoseconds and microseconds respectively. The time required to flip either dilute electronic or nuclear spins is orders of magnitude shorter than their decoherence times, leading to several schemes for quantum information processing with spin qubits. We investigate instead the novel regime where the eigenstates approximate 50:50 superpositions of the electronic and nuclear spin states forming "hybrid nuclear-electronic" qubits. Here we demonstrate quantum control of these states for the first time, using bismuth-doped silicon, in just 32 ns: this is orders of magnitude faster than previous experiments where pure nuclear states were used. The coherence times of our states are five orders of magnitude longer, reaching 4 ms, and are limited by the naturally-occurring 29Si nuclear spin impurities. There is quantitative agreement between our experiments and no-free-parameter analytical theory for the resonance positions, as well as their relative intensities and relative Rabi oscillation frequencies. In experiments where the slow manipulation of some of the qubits is the rate limiting step, quantum computations would benefit from faster operation in the hybrid regime.