Optical spin locking of a solid-state qubit

Abstract

Quantum control of solid-state spin qubits typically involves pulses in the microwave domain, drawing from the well-developed toolbox of magnetic resonance spectroscopy. Driving a solid-state spin by optical means offers a high-speed alternative, which in the presence of limited spin coherence makes it the preferred approach for high-fidelity quantum control. Bringing the full versatility of magnetic spin resonance to the optical domain requires full phase and amplitude control of the optical fields. Here, we imprint a programmable microwave sequence onto a laser field and perform electron spin resonance in a semiconductor quantum dot via a two-photon Raman process. We show that this approach yields full SU(2) spin control with over 98% π-rotation fidelity. We then demonstrate its versatility by implementing a particular multi-axis control sequence, known as spin locking. Combined with electron-nuclear Hartmann-Hahn resonances which we also report in this work, this sequence will enable efficient coherent transfer of a quantum state from the electron spin to the mesoscopic nuclear ensemble.

Building Blocks for Quantum Network Based on Group‐IV Split‐Vacancy Centers in Diamond

“…These studies emphasize the cruciality of ultra‐pure lattice environment (with [ and ) in realization of long coherence time, a critical condition to establish efficient spin–photon interface on integrated diamond nanophotonic platforms . On the other hand, the individually addressable electron spin in SiV − center provides a unique tool to study the dipolar coupling between the central spin and the surrounding nuclei, known as central spin problem …”

Optimal purification of a spin ensemble by quantum-algorithmic feedback

“…The approximate agreement between our measured optimum and this simple theoretical estimate confirms that the feedback is optimal close to the maximum achievable fidelity of the swap operation. Furthermore, our model informs us that our measured optimum is modified from the theoretical optimum by an optically induced electronic spin relaxation process whose rate is proportional to the power of the incident laser light enabling spin control [43]. Under our experimental conditions, this electronic relaxation rate is such that the electron spin is close to completely depolarized when the electron-nuclear exchange reaches its maximum at the π-time of the interaction.…”

“…Thus the feedback actuated by the electron corrects one nuclear-spin deviation at a time, and in doing so, purifies the state of the nuclear-spin system. An external magnetic field of 3.5 T along the z-direction Zeeman-splits the electron spin, which we control with all-optical electron-spin resonance (ESR) allowing for fast multi-axis control [43] (supplementary materials section IA). The system Hamiltonian, expressed in a frame rotating at the ESR drive frequency ω, is given by:…”

“…No measurement is made between steps 1 and 2, meaning the operation thus far is autonomous and reversible. In our QD system, we engineer the flipflop Hamiltonian from the A nc S z I x term by driving the central spin at Hartmann-Hahn resonance [43,48], Ω ≈ ω n , yielding Hff = Ω Sz +ω n I z − Anc 4 ( S+ I − + S− I + ) [49], where A ff = A nc /4.…”

“…The heterostructure of the wafer used in this work, which has been used in previous studies [36,43,46,52,54], consists of an InGaAs QD layer integrated into a Schottky diode structure which allows to control the charge state of the QD. At the bottom of the heterostructure is a distributed Bragg reflector to improve photon emission from the top surface.…”