CQT Colloquium by Mikhail Baranov, Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences

Title: Subwavelength optical barriers for cold atoms: creation and potential application
Date/Time: 22-Nov, 04:00PM
Venue: CQT Level 3 Seminar Room, S15-03-15

Abstract: The generation of subwavelength optical barriers on the scale of tens of nanometers, as conservative optical potentials for cold atoms, is discussed both theoretically and experimentally. In the proposed scheme they originate from nonadiabatic corrections to Born-Oppenheimer potentials for position-dependent “dark states” in atomic Λ configurations. The subwavelength optical barriers represent a “Kronig-Penney” potential, and I discuss the corresponding band structure including the effects of spontaneous emission and atom loss due to “bright” channels. Inclusion of an interparticle dipole-dipole interaction leads to formation of “domain wall molecules” and to unconventional Hubbard models with modulated in space interparticle interactions. As a brief discussion of potential applications, the subwavelength barrier can be used as a “splitter” to create a double-wire (or double-layer) with subwavelength spacing and, therefore, with substantially increased couplings as compared to ordinary optical lattices. As another application, specially designed subwavelength atomic internal-state spatial structures can be used for building an atomic scanning microscope with subwavelength resolution.

CQT Talk by Tobias Vogl, The Australian National University

Title: Next-generation single-photon sources for satellite-based quantum communication
Date/Time: 27-Nov, 04:00PM
Venue: CQT Level 3 Seminar Room, S15-03-15

Abstract: Color centers in solid state crystals have become a frequently used system for single-photon generation, advancing the development of integrated photonic devices for quantum optics and quantum communication applications. Recently, defects hosted by two-dimensional (2D) hexagonal boron nitride (hBN) attracted the attention of many researchers around the world, due to its chemical and thermal robustness as well as high single-photon luminosity at room temperature. Unlike for NV centers in diamond and other solid-state quantum emitters in 3D systems, the 2D crystal lattice of hBN allows for an intrinsically ideal extraction efficiency, as none of the emitters are embedded in any high refractive index material and are consequently not affected by Fresnel or total internal reflection. In addition, atomically-thin crystals can be integrated into photonic circuits easily. Here, we present recent advances in coupling this new type of emitter with nano-photonic structures in the Purcell regime. An increased collection efficiency and quantum yield, combined with off-resonant noise suppression and improvement of photophysics allow to use this single-photon source for realistic quantum key distribution experiments and other quantum information protocols. The device outperformes state-of-the-art decoy state QKD protocols. We also assess the usage on Nanosatellites due of the source's high temperature robustness as well as its SWaP (Size, Weight and Power) requirements and show results on our implementation on a 1U CubeSat. In addition to the single-photon source, the CubeSat is also equipped with a single-photon interferometer with which, if launched into space, we can test certain quantum gravity theories and physics beyond the standard model.

The Annual Symposium of the Centre for Quantum Technologies (CQT), Singapore

Date/Time: 24-Jan - 24-Jan
Venue: SFAH Auditorium, Level 2, Shaw Foundation Alumni House

On the occasion of CQT’s 11th anniversary, we invite you to join us for a symposium on quantum technologies with strong international and local speakers. We welcome all interested researchers and industry colleagues to the event on 24 January 2019. The one-day programme features talks and a panel discussion across a range of experimental and theoretical topics. Each year’s symposium will include different themes. This year’s programme has an emphasis on quantum computing and algorithms.

Website: https://cqt11.quantumlah.org/

CQT Talk by Rodney Van Meter, Keio University, Japan

Title: Three Short Pieces: Hijacking Quantum Repeaters, Quantum Byzantine Agreement, and Simulating the Quantum Internet
Date/Time: 19-Nov, 04:30PM
Venue: CQT Level 3 Seminar Room, S15-03-15

Abstract: In this combination talk, I will give a quick sketch of two recent results, and give a glimpse into the current status of our simulation efforts: The network impact of hijacking a quantum repeater Takahiko Satoh, Shota Nagayama, Takafumi Oka and Rodney Van Meter http://iopscience.iop.org/article/10.1088/2058-9565/aac11f/meta In quantum networking, repeater hijacking menaces the security and utility of quantum applications. To deal with this problem, it is important to take a measure of the impact of quantum repeater hijacking. We show the costs for repeater hijacking detection using distributed quantum state tomography and the amount of work loss and rerouting penalties caused by hijacking, and propose counter-measures. Resource-aware system architecture model for implementation of quantum aided Byzantine agreement on quantum repeater networks Mohammand Amin Taherkhani, Keivan Navi and Rodney Van Meter http://iopscience.iop.org/article/10.1088/2058-9565/aa9bb1/meta Quantum aided Byzantine agreement is an important distributed quantum algorithm with unique features in comparison to classical deterministic and randomized algorithms, requiring only a constant expected number of rounds in addition to giving a higher level of security. We require a quantum system architecture with 160 qubits per node, and error threshold $1.1\times {10}^{-6}$. We need to successfully distribute a total of 648 Bell pairs across the network, spread evenly between all pairs of nodes, to run the algorithm once. This framework can be considered a starting point for establishing a road-map for light-weight demonstration of a distributed quantum application on QRNs. Finally, I will give a short look into QUISP, our fourth-generation quantum repeater simulator, which is now in development. Our goal is to simulate a full Quantum Internet of 100 networks consisting of 100 nodes each. This will allow us to test protocol design choices for every aspect of the Quantum Internet, including interoperability mechanisms for use as the network evolves.

Rodney Van Meter received a B.S. in engineering and applied science from the California Institute of Technology in 1986, an M.S. in computer engineering from the University of Southern California in 1991, and a Ph.D. in computer science from Keio University in 2006. His current research centers on quantum computer architecture and quantum networking. Other research interests include storage systems, networking, and post-Moore's Law computer architecture. He is now an Associate Professor of Environment and Information Studies at Keio University's Shonan Fujisawa Campus. He is the Vice Dean of the Graduate School of Media and Governance, and the Vice Center Chair of Keio's new Quantum Computing Center. Dr. Van Meter is a member of AAAS, ACM and IEEE.