All-Optical Initialization, Readout, and Coherent Preparation of Single Silicon-Vacancy Spins in Diamond

Abstract

The silicon-vacancy (SiV − ) color center in diamond has attracted attention because of its unique optical properties. It exhibits spectral stability and indistinguishability that facilitate efficient generation of photons capable of demonstrating quantum interference. Here we show optical initialization and readout of electronic spin in a single SiV − center with a spin relaxation time of T 1 ¼ 2.4 AE 0.2 ms. Coherent population trapping (CPT) is used to demonstrate coherent preparation of dark superposition states with a spin coherence time of T ⋆ 2 ¼ 35 AE 3 ns. This is fundamentally limited by orbital relaxation, and an understanding of this process opens the way to extend coherence by engineering interactions with phonons. Hyperfine structure is observed in CPT measurements with the 29 Si isotope which allows access to nuclear spin. These results establish the SiV − center as a solid-state spin-photon interface. Coherent quantum systems which efficiently couple long-lived quantum memories to optical photons are a key resource for realizing quantum networks [1]. Color centers in diamond [2] are attractive candidates owing to unique properties of diamond, which include optical transparency and a high lattice quality that allows spin to function as long-lived quantum memory [3]. The negative silicon-vacancy (SiV − ) defect in diamond [4-6] has exceptional optical properties that facilitate efficient generation of indistinguishable photons from multiple distinct emitters [7]. Here we show optical initialization and readout of electronic spin in a single SiV − center with a spin relaxation time of T 1 ¼ 2.4 AE 0.2 ms. Two-photon resonance [8] is used to demonstrate coherent preparation of dark superposition states with a spin coherence time of T ⋆ 2 ¼ 35 AE 3 ns. This is shown to be limited by orbital relaxation that may be suppressed by engineering interactions with phonons. We present the first evidence of hyperfine interaction with a 29 Si nuclear spin in SiV − which can potentially be used as a memory qubit [9]. Quantum information processing efforts in diamond have mainly focused on the nitrogen-vacancy (NV − ) center because of its excellent spin properties at ambient conditions [10]. All-optical access to NV − spin is possible [11][12][13][14]; however, its large phonon sideband and spectral diffusion reduce coherent photon generation rates and limit the development of NV − quantum networks [15][16][17]. The main optical advantage provided by the SiV − center is that 70% of its fluorescence is concentrated in a sharp zero-phonon line (ZPL), making it ideal for single photon source applications [18,19]. It is spectrally stable at 737 nm, exhibits line widths limited by the excited state lifetime [20], and can be coupled to optical cavities [21,22]. Physically, the SiV − center consists of a single silicon atom replacing two carbon atoms in the diamond lattice, forming D 3d symmetry as illustrated in Fig. 1(a) [4][5][6]23]. This geometry makes the SiV − center insensitive to small electric fields [7] and th...

Optical Dependence of Electrically Detected Magnetic Resonance in Lightly Doped Si:P Devices

“…Isolated semiconductor dopants and defects offer long coherence times, robust and accurate quantum control and can be integrated into realistic device geometries. Some of the more intensively studied systems are nitrogen-and silicon-vacancy centers in diamond [1][2][3], various defects in silicon carbide [4,5], as well as group V donors in silicon such as phosphorus [6][7][8], arsenic [9] and bismuth [10].…”

Diamond Spins Shining Bright

“…These four spectral features correspond to the four possible transitions between the Zeeman-split electronic spin sublevels of the orbital branches involved in transition D (numbered D1-D4 with decreasing energy). A qualitatively identical pattern of four features was measured for transition C [25], allowing a determination of the Zeeman splittings illustrated in Fig. 1(d).…”

“…2(a)] was limited by laser intensity due to competition between the long spin relaxation and slow optical pumping rates on D1. Equivalent measurements with the field misaligned by about 20 degrees, where the PRL 2014 spin-flipping transition is stronger, demonstrated an initialization fidelity of at least 95% [25].…”

“…2(b). For a SiV − center misaligned about 20 degrees from the magnetic field, the spin relaxation time was measured to be T spin 1 ¼ 3.4 μs, and a 70-degree misalignment reduced this to T spin 1 ∼ 60 ns [25]. This sharp decrease in spin relaxation time is a direct result of the spin state mixing induced by the off-axis magnetic field, and is accompanied by peaks D1 and D4 starting to appear in excitation spectra without the need for a second repumping laser.…”

“…A diamond plate with f111g surfaces (see Ref. [25] for details of the synthesis) was cooled to around 5 K in a continuous flow cryostat, and imaged using a home-built confocal fluorescence microscope. Resonant excitation spectra of the four fine-structure transitions A-D [ Fig.…”