A throughput optimal scheduling policy for a quantum switch

We study a quantum switch that creates shared end-to-end entangled quantum states to multiple sets of users that are connected to it. Each user is connected to the switch via an optical link across which bipartite Bell-state entangled states are generated in each time-slot with certain probabilities, and the switch merges entanglements of links to create end-to-end entanglements for users. One qubit of an entanglement of a link is stored at the switch and the other qubit of the entanglement is stored at the user corresponding to the link. Assuming that qubits of entanglements of links decipher after one time-slot, we characterize the capacity region, which is defined as the set of arrival rates of requests for end-to-end entanglements for which there exists a scheduling policy that stabilizes the switch. We propose a Max-Weight scheduling policy and show that it stabilizes the switch for all arrival rates that lie in the capacity region. We also provide numerical results to support our analysis

Experimental Bounds on Classical Random Field Theories

Alternative theories to quantum mechanics motivate important fundamental tests of our understanding and descriptions of the smallest physical systems. Here, using spontaneous parametric downconversion as a heralded single-photon source, we place experimental limits on a class of alternative theories, consisting of classical field theories which result in power-dependent normalized correlation functions. In addition, we compare our results with standard quantum mechanical interpretations of our spontaneous parametric downconversion source over an order of magnitude in intensity. Our data match the quantum mechanical expectations, and do not show a statistically significant dependence on power, limiting on quantum mechanics alternatives which require power-dependent autocorrelation functions.Comment: 11pages, 2 figure

Effect of hyperfine structure on atomic frequency combs in Pr:YSO

Quantum memory will be a key component in future quantum networks, and atomic frequency combs (AFCs) in rare-earth-doped crystals are one promising platform for realizing this technology. We theoretically and experimentally investigate the formation of AFCs in Pr3+:Y2SiO5, with an overall bandwidth of 120 MHz and tooth spacing ranging from 0.1 MHz to 20 MHz, showing agreement between our calculations and measurements. We observe that the echo efficiency depends crucially on the AFC tooth spacing. Our results suggest approaches to developing a high-efficiency AFC quantum memory.Comment: 20 pages, 7 figure

Towards an efficient nanophotonic platform integrating quantum memories and single qubits based on rare-earth ions

The integration of rare-earth ions in an on-chip photonic platform would enable quantum repeaters and scalable quantum networks. While ensemble-based quantum memories have been routinely realized, implementing single rare-earth ion qubit remains an outstanding challenge due to its weak photoluminescence. Here we demonstrate a nanophotonic platform consisting of yttrium vanadate (YVO) photonic crystal nanobeam resonators coupled to a spectrally dilute ensemble of Nd ions. The cavity acts as a memory when prepared with spectral hole burning, meanwhile it permits addressing of single ions when high-resolution spectroscopy is employed. For quantum memory, atomic frequency comb (AFC) protocol was implemented in a 50 ppm Nd:YVO nanocavity cooled to 480 mk. The high-fidelity quantum storage of time-bin qubits is demonstrated with a 80% efficient WSi superconducting nanowire single photon detector (SNSPD). The small mode volume of the cavity results in a peak atomic spectral density of <10 ions per homogeneous linewidth, suitable for probing single ions when detuned from the center of the inhomogeneous distribution. The high-cooperativity coupling of a single ion yields a strong signature (20%) in the cavity reection spectrum, which could be detected by our efficient SNSPD. We estimate a signal-to-noise ratio exceeding 10 for addressing a single Nd ion with its 879.7nm transition. This, combines with the AFC memory, constitutes a promising platform for preparation, storage and detection of rare-earth qubits on the same ship

Atomic Resonance and Scattering

Contains reports on four research projects.U.S. Air Force - Office of Scientific Research (Grant AFOSR-76-2972)National Science Foundation (Grant CHE79-02967)National Science Foundation (Grant PHY79-09743)Joint Services Electronics Program (Contract DAAG29-78-C-0020)Joint Services Electronics Program (Contract DAAG29-80-C-0104

Atomic Resonance and Scattering

Contains reports on eight research projects.National Science Foundation (Grant PHY79-09743)National Bureau of Standards (Grant NB-8-NAHA-3017)Joint Services Electronics Program (Contract DAAG29-80-C-0104)National Science Foundation (Grant PHY82-10486)U.S. Navy - Office of Naval Research (Contract N00014-79-C-0183)National Science Foundation (Grant CHE79-02967-A04)U.S. Air Force - Office of Scientific Research (Contract AFOSR-81-0067)Joint Services Electronics Program (Contract DAAG29-83-K-0003

Atomic Resonance and Scattering

Contains reports on nine research projects.National Science Foundation (Grant PHY79-09743)National Science Foundation (Grant PHY82-10486)Joint Services Electronics Program (Contract DAAG29-83-K-0003)U.S. Navy - Office of Naval Research (Contract N00014-79-C-0183)National Bureau of Standards (Grant NB83-NAHA-4058)National Science Foundation (Grant CHE79-02967-A04)National Science Foundation (Grant PHY83-07172)Joint Services Electronics Program (Grant DAAG29-83-K-0003