Igal Bayn

Coherent spin control of a nanocavity-enhanced qubit in diamond

A central aim of quantum information processing is the efficient entanglement of multiple stationary quantum memories via photons. Among solid-state systems, the nitrogen-vacancy centre in diamond has emerged as an excellent optically addressable memory with second-scale electron spin coherence times. Recently, quantum entanglement and teleportation have been shown between two nitrogen-vacancy memories, but scaling to larger networks requires more efficient spin-photon interfaces such as optical resonators. Here we report such nitrogen-vacancy-nanocavity systems in the strong Purcell regime with optical quality factors approaching 10,000 and electron spin coherence times exceeding 200 μs using a silicon hard-mask fabrication process. This spin-photon interface is integrated with on-chip microwave striplines for coherent spin control, providing an efficient quantum memory for quantum networks.

Quantum nanophotonics in diamond [Invited]

The past two decades have seen great advances in developing color centers in diamond for sensing, quantum information processing, and tests of quantum foundations. Increasingly, the success of these applications as well as fundamental investigations of light–matter interaction depend on improved control of optical interactions with color centers—from better fluorescence collection to efficient and precise coupling with confined single optical modes. Wide ranging research efforts have been undertaken to address these demands through advanced nanofabrication of diamond. This review will cover recent advances in diamond nano- and microphotonic structures for efficient light collection, color center to nanocavity coupling, hybrid integration of diamond devices with other material systems, and the wide range of fabrication methods that have enabled these complex photonic diamond systems.

Fabrication of triangular nanobeam waveguide networks in bulk diamond using single-crystal silicon hard masks

A scalable approach for integrated photonic networks in single-crystal diamond using triangular etching of bulk samples is presented. We describe designs of high quality factor (Q = 2.51 × 106) photonic crystal cavities with low mode volume (Vm = 1.062 × (λ/n)3), which are connected via waveguides supported by suspension structures with predicted transmission loss of only 0.05 dB. We demonstrate the fabrication of these structures using transferred single-crystal silicon hard masks and angular dry etching, yielding photonic crystal cavities in the visible spectrum with measured quality factors in excess of Q = 3 × 103.

Nanofabrication on unconventional substrates using transferred hard masks

A major challenge in nanofabrication is to pattern unconventional substrates that cannot be processed for a variety of reasons, such as incompatibility with spin coating, electron beam lithography, optical lithography, or wet chemical steps. Here, we present a versatile nanofabrication method based on re-usable silicon membrane hard masks, patterned using standard lithography and mature silicon processing technology. These masks, transferred precisely onto targeted regions, can be in the millimetre scale. They allow for fabrication on a wide range of substrates, including rough, soft, and non-conductive materials, enabling feature linewidths down to 10 nm. Plasma etching, lift-off, and ion implantation are realized without the need for scanning electron/ion beam processing, UV exposure, or wet etching on target substrates.

Generation of Ensembles of Individually Resolvable Nitrogen Vacancies Using Nanometer-Scale Apertures in Ultrahigh-Aspect Ratio Planar Implantation Masks

A central challenge in developing magnetically coupled quantum registers in diamond is the fabrication of nitrogen vacancy (NV) centers with localization below ∼20 nm to enable fast dipolar interaction compared to the NV decoherence rate. Here, we demonstrate the targeted, high throughput formation of NV centers using masks with a thickness of 270 nm and feature sizes down to ∼1 nm. Super-resolution imaging resolves NVs with a full-width maximum distribution of 26 ± 7 nm and a distribution of NV-NV separations of 16 ± 5 nm.

Reactive ion etching: Optimized diamond membrane fabrication for transmission electron microscopy

Commonly used preparation method for thin diamond membranes by focused ion beam (FIB) techniques results in surface damage. Here, the authors introduce an alternative method based on reactive ion etching (RIE). To compare these methods, cross-sectional samples are produced in single crystal diamond, a material that has generated growing interest for a variety of applications. The samples are examined by Raman spectroscopy and high-resolution transmission electron microscopy (TEM). Raman spectra indicate that the crystalline structure of the RIE-processed diamond is preserved, while the FIB-processed diamond membrane has a broad-background sp2 feature. Atomic-resolution TEM imaging demonstrates that the RIE-based process produces no detectable damage, while the FIB-processed sample has an amorphous carbon layer of about 11 nm thick. These findings show that the RIE-based process allows the production of diamond TEM samples with reduced near-surface damage and can thus enable direct examination of growth de...

Targeted creation and Purcell enhancement of NV centers within photonic crystal cavities in single-crystal diamond

We demonstrate Purcell enhancement of single NV centers in L3 photonic crystal cavities made from high-purity single-crystal diamond. Furthermore, NV centers were created using an implantation mask in the cavity high field region.

Efficient integration of high-purity diamond nanostructures into silicon nitride photonic circuits

A high purity diamond nanowire with implanted nitrogen-vacancy centers (NVs) is integrated into a low-loss silicon nitride photonic circuit. NV fluorescence is coupled into and collected from the waveguide system, paving the way for on-chip read out and manipulation of qubits.

Towards Scalable Quantum Networks of Spin Qubits in Photonics Integrated Circuits

We discuss progress towards the development of on-chip quantum networks of multiple spin qubits in nitrogen vacancy (NV) centers in diamond. We report NV-nanocavity systems in the strong Purcell regime; implantation of NVs with nanometer-scale apertures, including into cavity field maxima; hybrid on-chip networks for integration of multiple functional NV-cavity systems; and scalable integration of superconducting nanowire single photon detectors on-chip.

Implantation of proximal NV clusters in diamond by lithographically defined silicon masks with 5 nm resolution

We present the fabrication of nitrogen-vacancy (NV) spin chains by implantation through a silicon mask on diamond. A minimum implantation aperture width of 5 nm is produced. Super-resolution measurements reveal NV lines 26 nm wide and minimal NV-pitch of 8 nm.