An integrated nanophotonic quantum register based on silicon-vacancy spins in diamond

Abstract

We realize an elementary quantum network node consisting of a silicon-vacancy (SiV) color center inside a diamond nanocavity coupled to a nearby nuclear spin with 100 ms long coherence times. Specifically, we describe experimental techniques and discuss effects of strain, magnetic field, microwave driving, and spin bath on the properties of this 2-qubit register. We then employ these techniques to generate Bell-states between the SiV spin and an incident photon as well as between the SiV spin and a nearby nuclear spin. We also discuss control techniques and parameter regimes for utilizing the SiV-nanocavity system as an integrated quantum network node. * These authors contributed equally to this work Recent work has established the silicon-vacancy colorcenter in diamond (SiV) as a promising candidate for quantum networking applications [19][20][21][22][23][24]. The SiV is an optically active point defect in the diamond lattice [25,26]. Its D 3d inversion symmetry results in a vanishing permanent electric dipole moment of the ground and excited states, rendering the transition insensitive to electric field noise typically present in nanostructures [27]. Recent work has independently shown that SiV centers in nanostructures display strong interactions with single photons [22] and that SiV centers at temperatures below 100 mK (achievable in dilution refrigerators) exhibit long coherence times [20,28]. While these results indicate the promising potential of the SiV center for future quantum network nodes, significant technical challenges must be overcome in order to combine these ingredients.In this paper, we outline the practical considerations and approaches needed to build a quantum network node with SiV centers in nanophotonic diamond cavities cou-arXiv:1907.13200v2 [quant-ph]

Experimental demonstration of memory-enhanced quantum communication

“…Experimental setup and device fabrication [19,33,36,37] for millikelvin nanophotonic cavity QED experiments with SiV centers are thoroughly described in a separate publication [38]. We perform all measurements in a dilution refrigerator (DR, BlueFors BF-LD250) with a base temperature of 20 mK.…”

“…In order to achieve high-fidelity operations we have to ensure that the laser frequency (which is not locked) is resonant with the SiV frequency f 0 (which is subject to the spectral diffusion [38]). To do that we implement a so-called preselection procedure, described in Table S1-2 and Fig.…”

“…S2a which corresponds to a single-photon Rabi frequency g = 8.38 ± 0.05 GHz, yielding the estimated cooperativity C = 4g 2 κγ = 105 ± 11. We use resonant MW pulses delivered via an on-chip coplanar waveguide (CWG) to coherently control the quantum memory [20,38]. First, we measure the spectrum of the spin-qubit transition by applying a weak, 10 µs-long microwave pulse of variable frequency, observing the optically-detected magnetic resonance (ODMR) spectrum presented in Fig.…”

“…We note that the spinqubit transition is split by the presence of a nearby 13 C . While coherent control techniques can be employed to utilize the 13 C as an additional qubit [20,38], we do not control or initialize it in this experiment. Instead, we drive the electron spin with strong microwave pulses at a frequency f Q such that both 13 C -state-specific transitions are addressed equally.…”

Simulation of topological phases with color center arrays in phononic crystals

“…For the SiV color center in diamond, the two lower sublevels (|g , |e ) can be defined as a spin qubit and coherently controlled by using microwave fields [80,81]. Moreover, in high-strain regime, the magnetic dipole transition between the ground-state levels of SiV centers can be directly driven with microwaves, which is already experimentally performed [85]. According to Eq.…”