Solid-state defect based quantum modules

Meysam Mohseni

Eric A. Bersin, Matthew E. Trusheim, Kevin C. Chen +4 more

Guoqing Wang, Changhao Li, Hao Tang +8 more

Solid-state defects are attractive platforms for quantum sensing and simulation, e.g., in exploring many-body physics and quantum hydrodynamics. However, many interesting properties can be revealed only upon changes in the density of defects, which instead is usually fixed in material systems. Increasing the interaction strength by creating denser defect ensembles also brings more decoherence. Ideally one would like to control the spin concentration at will while keeping fixed decoherence effects. Here, we show that by exploiting charge transport, we can take some steps in this direction, while at the same time characterizing charge transport and its capture by defects. By exploiting the cycling process of ionization and recombination of NV centers in diamond, we pump electrons from the valence band to the conduction band. These charges are then transported to modulate the spin concentration by changing the charge state of material defects. By developing a wide-field imaging setup integrated with a fast single photon detector array, we achieve a direct and efficient characterization of the charge redistribution process by measuring the complete spectrum of the spin bath with micrometer-scale spatial resolution. We demonstrate a two-fold concentration increase of the dominant spin defects while keeping the T 2 of the NV center relatively unchanged, which also provides a potential experimental demonstration of the suppression of spin flip-flops via hyperfine interactions. Our work paves the way to studying many-body dynamics with temporally and spatially tunable interaction strengths in hybrid charge–spin systems.

David Peter Divincenzo

Jason M. Smith, Brian Patton, Fabio Grazioso

Recent developments in the theory of measurement-based quantum computing reduce the problem of building a quantum computer to that of achieving high quality rotation and measurement of single qubits. The first generation of such machines may well therefore consist of individual modules each containing a single quantum system that embodies the qubit. The first demonstrations of entanglement of electronic qubits by measurement have been performed recently in ion traps. The leading contenders for physical qubits in the solid state are the negatively charged nitrogen-vacancy defect in diamond and the Stranski Krastanow quantum dot, each of which offers long electronic spin dephasing times and convenient spin-sensitive optical transitions. In this article we will compare the strengths and weaknesses of these two systems and discuss some of the challenges to be met in constructing a measurement based quantum computer in the solid state.

Serghey V. Vonsovsky, Mikhail I. Katsnelson