The efficient generation, coherent control, manipulation and measurement of quantum states of light and matter is at the core of quantum technologies. Hybrid quantum systems, where one combines the best parts of multiple individual quantum systems together without their weaknesses, are now seen as a way to engineer composite quantum systems with the properties one requires. This would in principle allow one to probe new physical regimes. However, the issue until recently has been that hybridization has not resulted in systems with superior properties. Recently however we [Nature Photonics 11, 3639 (2016)] have shown an increased coherence times in hybrid system is of composed nitrogen-vacancy centers strongly coupled to a superconducting microwave resonator. This demonstration has enabled this kind of hybrid system to enter the regime where quantum nonlinearities are present. We discuss several types of nonlinearity effects that can be naturally explored (bistability and superradiance). Our work paves the way for the creation of spin squeezed states, novel metamaterials, long-lived quantum multimode memories and solid-state microwave frequency combs. Further in the longer term it may enable the exploration of many-body phenomena in new cavity quantum electrodynamics experiments.
In this work, we describe a simple module that could be ubiquitous for quantum information based applications. The basic modules comprises a single NV<sup>-</sup> center in diamond embedded in an optical cavity, where the cavity mediates interactions between photons and the electron spin (enabling entanglement distribution and efficient readout), while the nuclear spins constitutes a long-lived quantum memories capable of storing and processing quantum information. We discuss how a network of connected modules can be used for distributed metrology, communication and computation applications. Finally, we investigate the possible use of alternative diamond centers (SiV/GeV) within the module and illustrate potential advantages.
We present new quantum repeater architectures based on optical modules with NV diamond centers to highlight how physical properties of these optical modules change the operations, performance and limitations of the quantum repeater systems.We focus on two different approaches to construct optical modules, and see how the properties of modules propagate to the total system. The first approach to construct the optical module is to utilize the conditional refection dependent on the electron state of the single NV center in the cavity, and the other approach is to use absorption induced teleportation from an incoming photon to the nuclear spin of the NV center.
To characterize a quantum repeater system, the processes and protocols associated with photons are important.As photons are not reliable as an information carrier, i.e. quantum manipulations associated with photons are not deterministic, and the protocols and manipulations rely on post-selection to keep the fidelity of the quantum information.Post-selection is essential in quantum communications based on photons to maintain the fidelity of the communication, however it restricts the architecture of the system to be tolerant to probabilistic gates. This factor is cost intensive and is the key for the architectures to be scalable.We show that the details of how the scalability of the architectures can be affected by physical parameters of the modules.
We present a quantum repeater architecture using nitrogen-vacancy (NV) diamond based quantum information devices. The NV-diamond based device consists of a single negatively charged NV (NV<sup>-</sup>) center and an optical cavity. The electron of the NV center is an interface to light to be used to distribute long-distance entanglement as well as entanglement bonds for cluster state operation at each nodes. The nuclear spin-1=2 of nitrogen 15 can be used as memory. Based on this device, A scheme with as small as 10 devices to a scalable architecture is constructed, showing the necessary node technology as well as the performance such quantum communication systems.
We present initial measurements of the dispersive index of refraction for sodium matter waves passing through argon. In addition, we describe a novel scheme for performing tomography on the longitudinal quantum state of particles in an atomic beam.
Atoms interacting with standing light waves are a model system for the propagation of waves in static and time varying periodic media. We present here experiments studying the coherent motion of atomic deBroglie waves in periodic potentials made from on and off resonant light. We observe anomalous transmission of atoms through resonant standing light waves and experimentally confirm that atoms fulfilling the Bragg condition form a standing matter wave pattern. We furthermore demonstrate how Bragg diffraction of atomic matter waves at a time-modulated thick standing light wave can be used to coherently shift the deBroglie frequency of the diffracted atoms. Our frequency shifter for atomic matter waves is similar to an acousto-optic frequency shifter for photons.