Robust nano-fabrication of an integrated platform for spin control in a tunable microcavity

Abstract

Coupling nitrogen-vacancy centers in diamond to optical cavities is a promising way to enhance the efficiency of diamond based quantum networks. An essential aspect of the full toolbox required for the operation of these networks is the ability to achieve microwave control of the electron spin associated with this defect within the cavity framework. Here, we report on the fabrication of an integrated platform for microwave control of an NV center electron spin in an open, tunable Fabry-Pérot microcavity. A critical aspect of the measurements of the cavity's finesse reveals that the presented fabrication process does not compromise its optical properties. We provide a method to incorporate a thin diamond slab into the cavity architecture and demonstrate control of the NV center spin. These results show the promise of this design for future cavity-enhanced NV center spin-photon entanglement experiments.Nitrogen-vacancy (NV) colour centers in diamond have emerged as attractive candidates for quantum photonic applications. Their electronic spin can be optically initialized, read out in a single shot 1 , and coherently manipulated with the use of microwave signals 2 . This spin-photon interface provides a platform for distant entanglement generation 3 , while additional coupling to nearby carbon-13 nuclear spins forms a multi-qubit quantum node 4-7 . These aspects make the NV center a good candidate for quantum network protocols 8-10 . The efficiency of entanglement generation between network nodes is currently limited by the NV center's low (≈ 3%) emission rate of the resonant zero-phonon line (ZPL) photons. This problem can be addressed by coupling NV centers to optical microcavities 11-23 , enhancing the ZPL emission rate and providing efficient photon extraction by means of the Purcell effect 24 . An appealing cavity design consists of an open, tunable Fabry-Pérot microcavity housing a large area diamond membrane [25][26][27] in which emitters retain their bulk-like properties 28 . The tunability of this design enables both spectral positioning of the cavity to be resonant with the emitter as well as selective lateral placement of the emitter within the center of the cavity mode. However, in order to use these emitters in quantum information protocols, microwave control must be integrated into the cavity architecture. Here, we present fabrication methods used to create a platform that integrates microwave control of an NV center spin within an optical cavity while maintaining the cavity's high finesse properties. While microwave addressing of a single NV center spin has already been realized in thin diamond slabs 29 and photonic crystal cavities 21 , this is the first demonstration of NV center spin addressing within a framework tailored to the implementation of a tunable microcavity.The cavity consists of a dimpled fiber tip and polished fused silica plate, both coated with a highly reflective dielectric mirror stack (Figure 1(A)). Microwave striplines and marker arrays are fabricated on the planar mirror surface...

Magnetic resonance imaging of spin-wave transport and interference in a magnetic insulator

“…To attach an NV-containing diamond to the YIG film, a small droplet of isopropanol was deposited onto the YIG, on top of which a diamond chip was placed, with the NV surface facing down. The diamond chip was gently pressed down until the isopropyl alcohol had evaporated ( 42 ). The resulting NV-YIG distance was measured to be 1.8(2) μm (see fig.…”

Spin Readout Techniques of the Nitrogen-Vacancy Center in Diamond

“…New designs and fabrication approaches that allow waveguides and cavities to be created directly from bulk diamond crystals [ 70 , 71 ] potentially offer a way forward, although the control of surface noise that causes deteriorated optical linewidths in nanophotonic structures remains a formidable challenge. One approach to avoiding these sources of noise is to use NVs embedded within diamond membranes of micron-scale thickness, which can be aligned within high-finesse fiber-based cavities, albeit with larger mode volumes ( Figure 2 d) [ 59 , 72 , 73 ].…”

“…Equation ( 26 ) represents the ideal case, assuming a cavity mode resonant with the relevant optical transition and an optical dipole located at the position of maximum field, aligned with its polarization axis. In practice, NV centers can be directly embedded in photonic crystal cavities fabricated from thin diamond membranes [ 59 , 68 , 69 , 73 , 80 ] or positioned close to cavities fabricated in another high-refractive-index material [ 78 , 79 , 81 ]. The prior method generally results in higher than the latter, due to increased spatial overlap between the NV center’s optical dipole and the cavity field [ 68 ].…”

“…The prior method generally results in higher than the latter, due to increased spatial overlap between the NV center’s optical dipole and the cavity field [ 68 ]. Most investigations have explored how the zero-phonon-line emission around 637 can be enhanced [ 59 , 68 , 69 , 73 , 78 ], since photons in this band are ultimately required for coherent spin-photon interfaces with NV centers. Meanwhile, potential effects on the spin-readout SNR for NV centers coupled to photonic crystal cavities remain relatively unexplored.…”

Tunable Open‐Access Microcavities for Solid‐State Quantum Photonics and Polaritonics

“…Bogdanovic et al. reported a fabrication process to include microwave stripes on the planar mirror of a fiber‐based open‐access microcavity embedded with diamond membranes in 2017, which enables the demonstration of NV spin control with microwaves …”