Abstract: A hybrid quantum system performs high-fidelity quantum state transduction between a superconducting (SC) microwave qubit and the ground state spin system of a solid-state artificial atom. This transduction is mediated via an acoustic bus connected by piezoelectric transducers to the SC microwave qubit. For SC circuit qubits and diamond silicon vacancy centers in an optimized phononic cavity, the system can achieve quantum state transduction with fidelity exceeding 99% at a MHz-scale bandwidth. By combining the complementary strengths of SC circuit quantum computing and artificial atoms, the hybrid quantum system provides high-fidelity qubit gates with long-lived quantum memory, high-fidelity measurement, large qubit number, reconfigurable qubit connectivity, and high-fidelity state and gate teleportation through optical quantum networks.

Abstract: Atoms and atom-like quantum emitters are promising for quantum sensing, computing, and communications. Lasers and microscopes enable high-fidelity quantum control of the atomic quantum bits (qubits). However, it is challenging to scale up individual quantum control to enough atomic quantum nodes for implementing useful and practical quantum algorithms. Here, we introduce methods and systems to holographically implement large-scale quantum circuits that individually address atomic quantum nodes. These methods enable implementation of quantum circuits over large, multi-dimensional arrays of atomic qubits at rates of thousands to millions of quantum circuit layers per second. The quantum circuit layers are encoded in multiplexed holograms displayed on a slow SLM and retrieved by fast interrogation to produce spatial distributions that operate on the qubit array.

Abstract: A method of nonblocking optical switching includes guiding a first optical beam from a first input to a first output via a first path through an optical switching fabric. The first path traverses a phase shifter disposed between a pair of cascaded Mach-Zehnder interferometers. The method also includes receiving a second optical beam for a second path intersecting with the first path through the optical switching fabric. The method also includes moving the first optical beam from the first path to a third path connecting the first input to the first output without intersecting the second path. The method also includes shifting a phase of the first optical beam, with the phase shifter, while moving the first optical beam from the first path to the third path to prevent the first optical beam from interfering with the second optical beam.

Abstract: A spatial light modulator (SLM) comprised of a 2D array of optically-controlled semiconductor nanocavities can have a fast modulation rate, small pixel pitch, low pixel tuning energy, and millions of pixels. Incoherent pump light from a control projector tunes each PhC cavity via the free-carrier dispersion effect, thereby modulating the coherent probe field emitted from the cavity array. The use of high-Q/V semiconductor cavities enables energy-efficient all-optical control and eliminates the need for individual tuning elements, which degrade the performance and limit the size of the optical surface. Using this technique, an SLM with 106 pixels, micron-order pixel pitch, and GHz-order refresh rates could be realized with less than 1 W of pump power.

Abstract: A process is provided for the high-yield heterogeneous integration of ‘quantum micro-chiplets’ (QMCs, diamond waveguide arrays containing highly coherent color centers) with an aluminum nitride (AlN) photonic integrated circuit (PIC). As an example, the process is useful for the development of a 72-channel defect-free array of germanium-vacancy (GeV) and silicon-vacancy (SiV) color centers in a PIC. Photoluminescence spectroscopy reveals long-term stable and narrow average optical linewidths of 54 MHz (146 MHz) for GeV (SiV) emitters, close to the lifetime-limited linewidth of 32 MHz (93 MHz). Additionally, inhomogeneities in the individual qubits can be compensated in situ with integrated tuning of the optical frequencies over 100 GHz. The ability to assemble large numbers of nearly indistinguishable artificial atoms into phase-stable PICs is useful for development of multiplexed quantum repeaters and general-purpose quantum computers.

Abstract: A process is provided for the high-yield heterogeneous integration of ‘quantum micro-chiplets’ (QMCs, diamond waveguide arrays containing highly coherent color centers) with an aluminum nitride (AlN) photonic integrated circuit (PIC). As an example, the process is useful for the development of a 72-channel defect-free array of germanium-vacancy (GeV) and silicon-vacancy (SiV) color centers in a PIC. Photoluminescence spectroscopy reveals long-term stable and narrow average optical linewidths of 54 MHz (146 MHz) for GeV (SiV) emitters, close to the lifetime-limited linewidth of 32 MHz (93 MHz). Additionally, inhomogeneities in the individual qubits can be compensated in situ with integrated tuning of the optical frequencies over 100 GHz. The ability to assemble large numbers of nearly indistinguishable artificial atoms into phase-stable PICs is useful for development of multiplexed quantum repeaters and general-purpose quantum computers.

Abstract: Systems based on atom and atom-like quantum emitters are promising platforms for quantum sensing, computing, and communications. State-of-the-art lasers and optical microscopy enable high-fidelity quantum control of the atomic quantum bits (qubits). However, it is challenging to scale up such individual quantum control to hundreds or thousands of atomic quantum nodes for implementing useful and practical quantum algorithms. Here, we introduce methods and systems to holographically implement large-scale quantum circuits that individually address atomic quantum nodes for various applications. These methods enable implementation of quantum circuits over large 2D and 3D arrays of atomic qubits at rates of thousands to millions of quantum circuit layers per second. The quantum circuit layers are encoded in multiplexed holograms displayed on a slow SLM and retrieved by fast interrogation to produce spatial distributions that operate on the qubit array.

Abstract: A spatial light modulator (SLM) comprised of a 2D array of optically-controlled semiconductor nanocavities can have a fast modulation rate, small pixel pitch, low pixel tuning energy, and millions of pixels. Incoherent pump light from a control projector tunes each PhC cavity via the free-carrier dispersion effect, thereby modulating the coherent probe field emitted from the cavity array. The use of high-Q/V semiconductor cavities enables energy-efficient all-optical control and eliminates the need for individual tuning elements, which degrade the performance and limit the size of the optical surface. Using this technique, an SLM with 106 pixels, micron-order pixel pitch, and GHz-order refresh rates could be realized with less than 1 W of pump power.

Abstract: Quantum information processing involves entangling large numbers of qubits, which can be realized as defect centers in a solid-state host. The qubits can be implemented as individual unit cells, each with its own control electronics, that are arrayed in a cryostat. Free-space control and pump beams address the qubit unit cells through a cryostat window. The qubit unit cells emit light in response to these control and pump beams and microwave pulses applied by the control electronics. The emitted light propagates through free space to a mode mixer, which interferes the optical modes from adjacent qubit unit cells for heralded Bell measurements. The qubit unit cells are small (e.g., 10 ?m square), so they can be tiled in arrays of up to millions, addressed by free-space optics with micron-scale spot sizes. The processing overhead for this architecture remains relatively constant, even with large numbers of qubits, enabling scalable large-scale quantum information processing.

Abstract: Using the Meissner effect in superconductors, demonstrated here is the capability to create an arbitrarily high magnetic flux density (also sometimes referred to as “flux squeezing”). This technique has immediate applications for numerous technologies. For example, it allows the generation of very large magnetic fields (e.g., exceeding 1 Tesla) for nuclear magnetic resonance (NMR), magnetic resonance imaging (MRI), the generation of controlled magnetic fields for advanced superconducting quantum computing devices, and/or the like. The magnetic field concentration/increased flux density approaches can be applied to both static magnetic fields (i.e., direct current (DC) magnetic fields) and time-varying magnetic fields (i.e., alternating current (AC) magnetic fields) up to microwave frequencies.

Abstract: A reflective spatial light modulator (SLM) made of an electro-optic material, such as barium titanate, in a one-sided Fabry-Perot resonator can provide phase and/or amplitude modulation with fine spatial resolution at speeds over a Gigahertz. The light is confined laterally within the electro-optic material/resonator layer stack with microlenses, index perturbations, or by patterning the layer stack into a two-dimensional (2D) array of vertically oriented micropillars. Alternatively, a photonic crystal guided mode resonator can provide vertical and lateral confinement of the resonant mode. In phase-only modulation mode, each pixel in the SLM can produce a ? phase shift under a bias voltage below 10 V, while maintaining nearly constant reflection amplitude. The methodology for designing this SLM could also be used to design other SLMs (for example, amplitude-only SLMs).

Abstract: A spatial light modulator (SLM) comprised of a 2D array of optically-controlled semiconductor nanocavities can have a fast modulation rate, small pixel pitch, low pixel tuning energy, and millions of pixels. Incoherent pump light from a control projector tunes each PhC cavity via the free-carrier dispersion effect, thereby modulating the coherent probe field emitted from the cavity array. The use of high-Q/V semiconductor cavities enables energy-efficient all-optical control and eliminates the need for individual tuning elements, which degrade the performance and limit the size of the optical surface. Using this technique, an SLM with 106 pixels, micron-order pixel pitch, and GHz-order refresh rates could be realized with less than 1 W of pump power.

Abstract: Many of the features of neural networks for machine learning can naturally be mapped into the quantum optical domain by introducing the quantum optical neural network (QONN). A QONN can be performed to perform a range of quantum information processing tasks, including newly developed protocols for quantum optical state compression, reinforcement learning, black-box quantum simulation and one way quantum repeaters. A QONN can generalize from only a small set of training data onto previously unseen inputs. Simulations indicate that QONNs are a powerful design tool for quantum optical systems and, leveraging advances in integrated quantum photonics, a promising architecture for next generation quantum processors.

Abstract: A two-photon logic gate introduces a phase shift between two photons using a Q-switched cavity with some nonlinearity. The two-photon logic gate catches photons in and releases photons from de-coupled cavity modes in response to electronic or photonic control signals. This “catch-and-release” two-photon gate can be formed in semiconductor photonic integrated circuit (PIC) that operates at room temperature. When combined with sources, linear circuits, other logic gates, and detectors, it can be used to make a quantum computer with up to 1000 error-corrected logical qubits on a cm2 PIC, with full qubit connectivity to avoid overhead. Two-qubit gate fidelity exceeding 99% is possible with near-term technology, and scaling beyond 99.9% is possible. Two-photon logic gates are also suitable for gate-based quantum digital computing and for analog quantum computing schemes, such as adiabatic quantum computing or quantum annealing.

Abstract: A filter-based color imaging array that resolves N different colors detects only 1/Nth of the incoming light. In the thermal infrared wavelength range, filtering loss is exacerbated by the lower sensor detectivity at infrared wavelengths than at visible wavelengths. To avoid loss due to filtering, most spectral imagers use bulky optics, such as diffraction gratings or Fourier transform interferometers, to resolve different colors. Fortunately, it is possible to avoid filtering loss without bulky optics: detect light with interleaved arrays of sub-wavelength-spaced antennas tuned to different wavelengths. An optically sensitive element inside each antenna absorbs light at the antenna's resonant wavelength. Metallic slot antennas offer high efficiency, intrinsic unidirectionality, and lower cross-talk than dipole or bowtie antennas. Graphene serves at the optically active material inside each antenna because its 2D nature makes it easily adaptable to this imager architecture.

Abstract: A method of nonblocking optical switching includes guiding a first optical beam from a first input to a first output via a first path through an optical switching fabric. The first path traverses a phase shifter disposed between a pair of cascaded Mach-Zehnder interferometers. The method also includes receiving a second optical beam for a second path intersecting with the first path through the optical switching fabric. The method also includes moving the first optical beam from the first path to a third path connecting the first input to the first output without intersecting the second path. The method also includes shifting a phase of the first optical beam, with the phase shifter, while moving the first optical beam from the first path to the third path to prevent the first optical beam from interfering with the second optical beam.

Abstract: Typically, quantum systems are very sensitive to environmental fluctuations, and diagnosing errors via measurements causes unavoidable perturbations. Here, an in situ frequency-locking technique monitors and corrects frequency variations in single-photon sources based on resonators. By using the classical laser fields used for photon generation as probes to diagnose variations in the resonator frequency, the system applies feedback control to correct photon frequency errors in parallel to the optical quantum computation without disturbing the physical qubit. Our technique can be implemented on a silicon photonic device and with sub 1 pm frequency stabilization in the presence of applied environmental noise, corresponding to a fractional frequency drift of <1% of a photon linewidth. These methods can be used for feedback-controlled quantum state engineering.

Abstract: An integrated optical beam steering device includes a planar dielectric lens that collimates beams from different inputs in different directions within the lens plane. It also includes an output coupler, such as a grating or photonic crystal, that guides the collimated beams in different directions out of the lens plane. A switch matrix controls which input port is illuminated and hence the in-plane propagation direction of the collimated beam. And a tunable light source changes the wavelength to control the angle at which the collimated beam leaves the plane of the substrate. The device is very efficient, in part because the input port (and thus in-plane propagation direction) can be changed by actuating only log2 N of the N switches in the switch matrix. It can also be much simpler, smaller, and cheaper because it needs fewer control lines than a conventional optical phased array with the same resolution.

Abstract: A light-trapping geometry enhances the sensitivity of strain, temperature, and/or electromagnetic field measurements using nitrogen vacancies in bulk diamond, which have exterior dimensions on the order of millimeters. In an example light-trapping geometry, a laser beam enters the bulk diamond, which may be at room temperature, through a facet or notch. The beam propagates along a path inside the bulk diamond that includes many total internal reflections off the diamond's surfaces. The NVs inside the bulk diamonds absorb the beam as it propagates. Photodetectors measure the transmitted beam or fluorescence emitted by the NVs. The resulting transmission or emission spectrum represents the NVs' quantum mechanical states, which in turn vary with temperature, magnetic field strength, electric field strength, strain/pressure, etc.

Abstract: A method includes applying, to a sample exhibiting optical scattering and having a emission particles distributed therein that exhibit spin-dependent fluorescence, a magnetic field to shift a resonance frequency of each emission particle in a position-dependent manner. The method also includes exciting the sample with an excitation beam that causes at least one emission particle to emit spin-dependent fluorescence and detecting the emitted spin-dependent fluorescence. The method also includes estimating a position of the emission particle(s) within the sample based on the spin-dependent fluorescence, the resonance frequency, and the magnetic field. The method also includes estimating optical transmission information for the sample based on a wavefront of the excitation beam and the estimated position. The optical transmission information including a measure of an optical field at each position of an emission particle.