All-optical control of a solid-state spin using coherent dark states

Abstract

The study of individual quantum systems in solids, for use as quantum bits (qubits) and probes of decoherence, requires protocols for their initialization, unitary manipulation, and readout. In many solid-state quantum systems, these operations rely on disparate techniques that can vary widely depending on the particular qubit structure. One such qubit, the nitrogen-vacancy (NV) center spin in diamond, can be initialized and read out through its special spin-selective intersystem crossing, while microwave electron spin resonance techniques provide unitary spin rotations. Instead, we demonstrate an alternative, fully optical approach to these control protocols in an NV center that does not rely on its intersystem crossing. By tuning an NV center to an excited-state spin anticrossing at cryogenic temperatures, we use coherent population trapping and stimulated Raman techniques to realize initialization, readout, and unitary manipulation of a single spin. Each of these techniques can be performed directly along any arbitrarily chosen quantum basis, removing the need for extra control steps to map the spin to and from a preferred basis. Combining these protocols, we perform measurements of the NV center's spin coherence, a demonstration of this full optical control. Consisting solely of optical pulses, these techniques enable control within a smaller footprint and within photonic networks. Likewise, this unified approach obviates the need for both electron spin resonance manipulation and spin addressability through the intersystem crossing. This method could therefore be applied to a wide range of potential solid-state qubits, including those which currently lack a means to be addressed. quantum control | quantum optics | semiconductor defects | spintronics T o explore control of individual quantum states, our experiments exploit coherent dark resonances that occur in a basic quantum mechanical-level configuration known as a lambda (Λ) system. This configuration, consisting of two lower energy states coherently coupled to a single excited state, has been observed in a wide array of systems including atoms (1), trapped ions, diamond nitrogenvacancy (NV) centers (2-4), quantum dots (5), superconducting phase quantum bits (qubits) (6), and optomechanical resonators (7). In trapped ions, Λ systems can additionally be exploited to drive stimulated Raman transitions (SRTs) providing unitary rotations of the qubit state (8, 9). This versatile structure also forms the framework for a variety of other important advances in quantum science such as electromagnetically induced transparency (10), slow light (11), atomic clocks (12), laser cooling (13), and spin-photon entanglement (14).Here, we use time-resolved methods and quantum state tomography to explore the dynamics of various optically driven processes within a solid-state Λ system (Fig. 1A). This allows us to demonstrate three all-optical quantum control (9, 15, 16) protocols for a single NV center: initialization, unitary rotation, and readout of its spin state. Our Λ s...

Decay of the rotary echoes for the spin of a nitrogen-vacancy center in diamond

“…Among these systems, the nitrogen-vacancy (NV) centers in diamond exhibit a set of particularly desirable features: individual centers can be initialized and read out optically, 1-4 possess naturally long coherence times even at room temperature, [5][6][7] and can be controlled 8 using magnetic fields, 9-12 optical excitations, [13][14][15][16][17] and electric fields. [18][19][20] As a result, the NV centers have attracted much attention as prospective qubits for quantum information processing, 4,7,15,16,[21][22][23][24][25] and as nanoscale sensors.…”

Silicon vacancy center in4H-SiC: Electronic structure and spin-photon interfaces

“…4(b). This three-level system can be used in numerous quantum applications and demonstrations, including coherent population trapping [43], optical spin qubit rotations [44,45] and generation of spin-photon entanglement [2,46] with applications in quantum repeaters [47]. In summary, we addressed the crucial need of calculating the multi-particle fine structure of the silicon vacancy defect in SiC.…”

All-optical control of a single electron spin in diamond

“…The complex level structure and selection rules of the NV center's optical transitions offer a rich and flexible set of possibilities for coherent all-optical control of all three spin sublevels. Past experiments have demonstrated optical spin manipulation under a large magnetic field or two-photon Rabi oscillations and stimulated Raman adiabatic passage (STIRAP) on microsecond timescales [13][14][15].In this Letter, we demonstrate complete all-optical coherent manipulation of the NV spin states. Importantly, initialization and readout of the spin states are also performed all-optically, providing a full set of experimental techniques that eliminates the need for microwave addressing.…”

“…We next explore coherent transfer of population between the |0 and |±1 states. This requires the coherent control of non-spin-preserving cross transitions between the ground and excited states [14,23]. We present spectroscopy and characterization of the tripod system formed between the |A 2 excited state and all three ground state levels in the same low-strain NV center as above.…”

“…The complex level structure and selection rules of the NV center's optical transitions offer a rich and flexible set of possibilities for coherent all-optical control of all three spin sublevels. Past experiments have demonstrated optical spin manipulation under a large magnetic field or two-photon Rabi oscillations and stimulated Raman adiabatic passage (STIRAP) on microsecond timescales [13][14][15].…”