Reseach associate (postdoctral researcher), Macquarie University
Designing new protocols for transfer of non-classical light beams between frequencies
Quantum computers are envisioned as distributed system, in which numerous nodes, capable of elementary quantum computations, collaborate extensively with each other to perform challenging computational tasks. To communicate, the nodes encode the results of their operations into photons, or quanta of light, and send them to other nodes. Over the last few years, tremendous effort from numerous research groups has brought us closer to realizing various architectures of the nodes, for example by using superconducting circuits or trapped ions. Our research, focused on the interface between these technologies, aims to increase the efficiency and the speed of the communication between non-identical nodes.
How do we plan to do this? Let us consider a simple analogy for a linear optical communication. Much like a simple message transferred by a line of people whispering into the neighbour's ear, photons sent into a linear optical waveguide can propagate over long distances, with little loss to the information content of the message. In this picture, if the frequencies of photons generated by the source node, and accepted by the destination node, differ, that the message has to be additionally translated between two languages (frequencies). The simplest approach would be to place two translators, or interfaces, at the ends of the communication channel. We propose an alternative approach, which relies on non-linear waveguides, which can themselves modify the frequencies of photons passing through the waveguide. Such systems would preserve the high quality of the communication channel, while eliminating the time-consuming process of translating the message. In our work we show how to realize such protocols in realistic physical systems.
With the research on different implementations of the quantum nodes progressing quickly, we hope that this work will provide the tools to interface these architectures, and later on, offer a reliable communication technology for the quantum internet.
Abstract: Efficient interfaces between photons and quantum emitters form the basis for quantum networks and enable optical nonlinearities at the single-photon level. We demonstrate an integrated platform for scalable quantum nanophotonics based on silicon-vacancy (SiV) color centers coupled to diamond nanodevices. By placing SiV centers inside diamond photonic crystal cavities, we realize a quantum-optical switch controlled by a single color center. We control the switch using SiV metastable states and observe optical switching at the single-photon level. Raman transitions are used to realize a single-photon source with a tunable frequency and bandwidth in a diamond waveguide. By measuring intensity correlations of indistinguishable Raman photons emitted into a single waveguide, we observe a quantum interference effect resulting from the superradiant emission of two entangled SiV centers.
Pub.: 16 Oct '16, Pinned: 19 Nov '17
Abstract: Strong non-linear interactions between photons enable logic operations for both classical and quantum-information technology. Unfortunately, non-linear interactions are usually feeble and therefore all-optical logic gates tend to be inefficient. A quantum emitter deterministically coupled to a propagating mode fundamentally changes the situation, since each photon inevitably interacts with the emitter, and highly correlated many-photon states may be created. Here we show that a single quantum dot in a photonic-crystal waveguide can be used as a giant non-linearity sensitive at the single-photon level. The non-linear response is revealed from the intensity and quantum statistics of the scattered photons, and contains contributions from an entangled photon–photon bound state. The quantum non-linearity will find immediate applications for deterministic Bell-state measurements and single-photon transistors and paves the way to scalable waveguide-based photonic quantum-computing architectures.
Pub.: 23 Oct '15, Pinned: 19 Nov '17
Abstract: Author(s): Yariv Yanay, Jack C. Sankey, and Aashish A. ClerkOptomechanical systems are typically affected by backaction noise, hindering their applicability to quantum measurements. While previous studies suggested that the effect could be completely suppressed, a thorough analysis taking into account realistic conditions shows that this is not the general case.[Phys. Rev. A 93, 063809] Published Wed Jun 08, 2016Optomechanical systems are typically affected by backaction noise, hindering their applicability to quantum measurements. While previous studies suggested that the effect could be completely suppressed, a thorough analysis taking into account realistic conditions shows that this is not the general case.
Pub.: 08 Jun '16, Pinned: 19 Nov '17
Abstract: We present a multimode Hamiltonian formulation for the problem of opto-acoustic interactions in optical waveguides. We establish a Hamiltonian representation of the acoustic field and then introduce a full system with a simple opto-acoustic coupling that includes both photoelastic/electrostrictive and radiation pressure/moving boundary effects. The Heisenberg equations of motion are used to obtain coupled mode equations for quantized envelope operators for the optical and acoustic fields. We show that the coupling coefficients obtained coincide with those established earlier, but our formalism provides a much simpler demonstration of the connection between radiation pressure and moving boundary effects than in previous work [C. Wolff et al, Physical Review A 92, 013836 (2015)].
Pub.: 03 Sep '15, Pinned: 31 Oct '17
Abstract: We describe a quantum state transfer protocol, where a quantum state of photons stored in a first cavity can be faithfully transferred to a second distant cavity via an infinite 1D waveguide, while being immune to arbitrary noise (e.g., thermal noise) injected into the waveguide. We extend the model and protocol to a cavity QED setup, where atomic ensembles, or single atoms representing quantum memory, are coupled to a cavity mode. We present a detailed study of sensitivity to imperfections, and apply a quantum error correction protocol to account for random losses (or additions) of photons in the waveguide. Our numerical analysis is enabled by matrix product state techniques to simulate the complete quantum circuit, which we generalize to include thermal input fields. Our discussion applies both to photonic and phononic quantum networks.
Pub.: 15 Apr '17, Pinned: 31 Oct '17
Abstract: Trapping light with noble metal nanostructures overcomes the diffraction limit and can confine light to volumes typically on the order of 30 cubic nanometers. We found that individual atomic features inside the gap of a plasmonic nanoassembly can localize light to volumes well below 1 cubic nanometer ("picocavities"), enabling optical experiments on the atomic scale. These atomic features are dynamically formed and disassembled by laser irradiation. Although unstable at room temperature, picocavities can be stabilized at cryogenic temperatures, allowing single atomic cavities to be probed for many minutes. Unlike traditional optomechanical resonators, such extreme optical confinement yields a factor of 10(6) enhancement of optomechanical coupling between the picocavity field and vibrations of individual molecular bonds. This work sets the basis for developing nanoscale nonlinear quantum optics on the single-molecule level.
Pub.: 16 Nov '16, Pinned: 31 Oct '17
Abstract: Plasmon-enhanced Raman scattering can push single-molecule vibrational spectroscopy beyond a regime addressable by classical electrodynamics. We employ a quantum electrodynamics (QED) description of the coherent interaction of plasmons and molecular vibrations that reveal the emergence of nonlinearities in the inelastic response of the system. For realistic situations, we predict the onset of phonon-stimulated Raman scattering and a counter-intuitive dependence of the anti-Stokes emission on the frequency of excitation. We further show that this novel QED framework opens a venue to analyze the correlations of photons emitted at a plasmonic cavity.
Pub.: 21 May '16, Pinned: 31 Oct '17
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