Silicon-Vacancy Spin Qubit in Diamond: A Quantum Memory Exceeding 10 ms with Single-Shot State Readout

Abstract

The negatively-charged silicon-vacancy (SiV − ) color center in diamond has recently emerged as a promising system for quantum photonics. Its symmetry-protected optical transitions enable creation of indistinguishable emitter arrays and deterministic coupling to nanophotonic devices. Despite this, the longest coherence time associated with its electronic spin achieved to date (∼ 250 ns) has been limited by coupling to acoustic phonons. We demonstrate coherent control and suppression of phonon-induced dephasing of the SiV − electronic spin coherence by five orders of magnitude by operating at temperatures below 500 mK. By aligning the magnetic field along the SiV − symmetry axis, we demonstrate spin-conserving optical transitions and single-shot readout of the SiV − spin with 89% fidelity. Coherent control of the SiV − spin with microwave fields is used to demonstrate a spin coherence time T2 of 13 ms and a spin relaxation time T1 exceeding 1 s at 100 mK. These results establish the SiV − as a promising solid-state candidate for the realization of quantum networks.Quantum networks require the ability to store quantum information in long-lived memories, to efficiently interface these memories with optical photons and to provide quantum nonlinearities required for deterministic quantum gate operations [1,2]. Even though key building blocks of quantum networks have been demonstrated in various systems [3,4], no solid-state platform has satisfied these requirements. Over the past decade, solid-state quantum emitters with stable spin degrees of freedom such as charged quantum dots and nitrogenvacancy (NV) centers in diamond have been investigated for the realization of quantum network nodes [5]. While quantum dots can be deterministically interfaced with optical photons [6], their quantum memory time is limited to the µs scale [7] due to interactions with their surrounding nuclear spin bath. In contrast, NV centers have an exceptionally long-lived quantum memory [8] but suffer from weak, spectrally unstable optical transitions [9]. Despite impressive proof-of-concept experimental demonstrations with these systems [10,11], scaling to a large number of nodes is limited by the challenge of identifying suitable quantum emitters with the combination of strong, homogeneous and coherent optical transitions and long-lived quantum memories.The negatively-charged silicon-vacancy (SiV − ) has recently been shown to have bright, narrowband optical transitions with a small inhomogeneous broadening [12,13]. The optical coherence of the SiV − is protected by its inversion symmetry [14], even in nanostructures [15]. These optical properties were recently used to show strong interactions between single photons and single SiV − centers and to probabilistically entangle two SiV − centers in a single nanophotonic device [16]. At 4 K, however, the SiV − spin coherence is limited to ∼ 100 ns due to coupling to the phonon bath, mediated by the spin-orbit interaction [17][18][19][20][21].In this Letter, we demonstrate high-fidelity coherent ...

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

“…At cryogenic temperature and zero magnetic field, the transition between these energy levels lead to a characteristic four‐line emission pattern in ZPL spectrum of SiV − , GeV − , SnV − , and PbV − centers, as shown in Figure c. These optically allowed transitions form a double‐Λ system, which has been utilized to realize orbital‐based coherent control schemes . An interesting observation is that the transition energy of the split‐vacancy center does not follow a monotonically linear increase with increasing the atomic number of group‐IV atom.…”

“…Ref. [] with , , 13 C, whereas for 1.1% 13 C. In ref. [], for , ; …”

“…These remarkable achievements, in turn, justify the advantages of diamond as host material for spin qubits: the wide bandgap of diamond allows the formation of deep impurity levels by the defects, and the well separation from the band edges effectively reduces the number of channels for spin decay. In addition, 12 C, the main constituent isotope of diamond with a natural abundance of 98.93%, holds zero nuclear spin, which offers an opportunity to completely quench the hyperfine interactions between the confined spin and host nuclei by depleting the concentration of 13 C () in diamond …”

“…Split‐vacancy color centers in diamond drop into this category by demonstrating a bright fluorescence with high ZPL concentration, low spectral diffusion, and minimal blinking . Together with a short radiative lifetime and long spin coherence time (on the order of ms), these single‐photon emitters emerge as promising platforms for applications in various fields of quantum technology, for examples, high‐resolution temperature sensor, GHz on‐demand single‐photon source, quantum registers, and long‐lived quantum memories by coupling to a nuclear spin (e.g., 29 Si for SiV − center).…”

Super-Resolution Localization and Readout of Individual Solid State Qubits

“…mation applications [41,49,50]; while subject to weaker broadening due to their symmetry, they may still prove distinguishable enough to apply our technique. Beyond diamond, defect centers in other materials such as silicon carbide [51], gallium nitride [52], or rare-earth ions in solids [53,54] could hold promise, as well as artificial atoms like quantum dots [55][56][57], all of which exhibit appreciable distributions of resonance frequencies.…”