Session Y43: Advances in the Quantum Control of Single Spins in Semiconductors

Multi-node quantum networks based on spins and photons

TBD   

Spin and Orbital Resonance Driven by a Mechanical Resonator

I describe our experiments to drive spin and orbital resonance of single diamond nitrogen-vacancy (NV) centers using the gigahertz-frequency strain oscillations produced within a diamond acoustic resonator. Strain-based coupling between a resonator and a defect center takes advantage of intrinsic and reproducible coupling mechanisms while maintaining compatibility with conventional magnetic and optical techniques, thus providing new functionality for quantum-enhanced sensing and quantum information processing. Using a spin-strain interaction at room temperature, we demonstrate coherent spin control [1] and spin coherence protection [2]. At cryogenic temperatures, we use orbital-strain interactions driven by a diamond acoustic resonator to examine multi-phonon orbital resonance of a single NV center [3]. We drive a strong mechanical modulation of the orbital state energies in the side-band resolved limit and produce nine orders of coherent Raman sidebands. When we match the resonator frequency to half of the orbital splitting, we demonstrate resonance between the orbital states using a transverse orbital-strain interaction. The resulting dressed orbital states display Autler-Townes splitting as a function of resonator amplitude that is well-described by a 2-phonon resonance process. Finally, we discuss orbital decoherence protection as means of engineering NV centers to be a better spin-photon interface as a potential application of these techniques.
1. E. R. MacQuarrie et al., Optica 2, 233 (2015).
2. E. R. MacQuarrie et al., Phys. Rev. B 92, 224419 (2015).
3. H. Chen et al., Phys. Rev. Lett. 120, 167401 (2018).
  

Probing spin-phonon interactions in semiconductors with x-rays and Gaussian acoustics

Coupling defect spins to phonons provides routes to new quantum control methods, coherence protection, and integrating spin qubits with quantum transducers. Silicon carbide (SiC) substrates host optically addressable point defects with long-lived electronic spin registers. Additionally, SiC is a low loss acoustic material and supports wafer-scale fabrication techniques, making SiC an ideal material for hybrid spin-mechanical systems. We fabricate surface acoustic wave (SAW) resonators taking advantage of isotropic acoustic propagation properties to construct simple Gaussian geometries, which focus strain and minimize diffraction losses. We directly image the mechanical mode with nanometer-scale spatial resolution by using hard x-ray diffraction microscopy and frequency matching a SAW to the timing structure of a synchrotron [1]. The SAW resonators are then utilized for coherent manipulation of divacancy electron spin ensembles in the SiC. We demonstrate all-optical detection of acoustic paramagnetic resonance, which enables quantum sensing of phonons without magnetic microwaves. In addition, we measure coherent magnetically forbidden spin transitions with Autler-Townes splittings and Rabi oscillations on the divacancy spins, as well as show spatial mapping of spin driving which reveals spin coupling to shear [2]. Our model, comprising of ab initio calculations for the spin-strain coupling parameters, captures the salient features of the physics. These results offer a basis for three-level spin system control with phonons and paths to combining spin registers with nanomechanical devices.

[1] S. J. Whiteley et al., arXiv:1808.04920 (2018).
[2] S. J. Whiteley et al., arXiv:1804.10996 (2018).

In collaboration with G. Wolfowicz, C. P. Anderson, A. Bourassa, H. Ma, M. Ye, G. Koolstra, K. J. Satzinger, M. V. Holt, F. J. Heremans, A. N. Cleland, D. I. Schuster, G. Galli, D. D. Awschalom   

Quantum nano-photonics with rare-earth-doped materials

I present quantum nano-photonic devices based on nanophotonic resonators
coupled to rare-earth-ions in crystals. The rare-earth ions exhibit long coherence
times on optical and microwave transitions, which makes them suitable for various
quantum light-matter interfaces line quantum memories, single quantum bits and
optical to microwave quantum transducers. We demonstrate on-chip optical
quantum memories based on atomic frequency combs and optically addressable
quantum bits based on single rare-earth ions where the quantum state can be
mapped on Zeeman or hyperfine levels with long coherence time. Our solid-state
nano-photonic quantum light-matter interfaces can be integrated with other chip-
scale photon source and detector devices for multiplexed quantum and classical
information processing at the nodes of quantum networks.   

Theory of electrical readout of deep defect qubits in solids

Paramagnetic color centers with deep levels in the gap are candidates to realize qubits in solids, in particular, those color centers that show spin-dependent fluorescence that can be employed to initialize and readout the electron spin of single color centers, first demonstrated for the nitrogen-vacancy (NV) center in diamond [1]. It has been shown [2] that optical excitation can also lead to ionization of NV center that is also spin dependent. The resultant carriers, i.e., the photocurrent can be collected that is the ground of photocurrent detected magnetic resonance (PDMR).
In my talk, I will show the power and significance of ab initio atomistic simulation techniques that can provide deep insight into the microscopic mechanisms behind the observed phenomena, and how it can be applied to optimize the conditions of qubit measurements. In particular, I will show how ab initio theory can explain the two-photon ionization of NV centre [3] that is the base of PDMR measurements. Intricate details of back ionization reveal the optical spinpolarization process in NV centre [4] under continuous green laser excitation. Theory predicted that two-color excitation will increase the signal-to-noise ratio of PDMR signal of NV center in diamond that was confirmed in experiment [5].
We will discuss very prospective deep color centers, divacancies in silicon carbide [6,7], what could be the experimental conditions to realize PDMR signal from these qubits in this technologically mature semiconductor.

[1] A. Gruber et al., Science 276, 2012-2014 (1997)
[2] E. Bourgeois et al., Nat. Com. 6, 8577 (2015)
[3] P. Siyushev et al., Phys. Rev. Lett. 110, 167402 (2013)
[4] G. Thiering and A. Gali, Phys. Rev. B 98, 085207 (2018)
[5] E. Bourgeois et al., Phys. Rev. B 95, 041402(R) (2017)
[6] A. Gali, phys. stat. sol. b 248, 1337 (2011)
[7] W. E. Koehl et al, Nature 479, 84 (2011)