Program

SESSION 13: Atomic, molecular, optical physics (experiment) (Pavilion I - III)

Chair: Poul Jessen (Arizona)
3:15 pm - 3:45 pmMichael Gould, Fu group (Washington)
Enhanced emission of zero-phonon line photons from a single nitrogen-vacancy center in diamond

Abstract. We demonstrate efficient, resonantly enhanced collection of zero-phonon line (ZPL) photons from a single nitrogen-vacancy (NV) center in diamond. The near-surface NV center is optically coupled to an integrated gallium-phosphide-on-diamond (GaP-on-diamond) disk resonator, which is coupled to an output bus waveguide. We estimate a total collection rate of 3.2 x 10^5 ZPL photons into the bus waveguide. This corresponds to a quantum efficiency of approximately 4.5%, significantly higher than the 3% theoretical limit without the use of resonant enhancement. The device was fabricated on a GaP-on-diamond chip, alongside a large number of other integrated photonic devices. These include vertical grating couplers with average coupling efficiencies of 17%, low-loss single-mode waveguides and low-loss directional couplers. This work puts the platform in a strong position to enable fully integrated NV-NV entanglement generation, at rates several orders of magnitude larger than what has been demonstrated in literature.

3:45 pm - 4:15 pm Tian Zhong, Faraon Group (IQIM, Caltech)
Broadband nanophotonic quantum interface with a cavity-protected rare-earth ensemble

Abstract. Ensembles of solid-state optical emitters are at the core of hybrid quantum interfaces between spins, optical, and microwave photons. To transfer information at quantum level, decoherence resulting from ensemble inhomogeneous broadening is currently suppressed using optical spin rephrasing techniques based on spectral hole burning, which require long preparation steps and reduce the interface bandwidth. We demonstrate that a solid-state ensemble of neodymium rare-earth ions strongly coupled to a photonic crystal resonator exhibits polaritons with strongly suppressed decoherence via the cavity protection phenomenon. Without using preparation steps, frequency qubits are stored and retrieved from the two polaritons with 98.7% fidelity and 50GHz bandwidth. The polaritons are supperadiant modes with emission rates >10^6 greater than uncoupled rare-earth ions, which enable ultra-fast (20 ps) control of the neodymium ensemble. Combined with long-lived spin-wave storage in rare-earth crystals, these results enable always-ready, on-demand, high-bandwidth quantum memories.

4:15 pm - 4:45 pmHector Sosa Martinez, Jessen group (Arizona)
Optimal strategies for quantum state and process tomography: efficiency versus robustness

Abstract. To build useful quantum hardware one needs good ways to characterize its behavior. In principle quantum tomography (QT) is an ideal tool, capable of providing complete information about an unknown state (QST) or process (QPT). In practice, the protocols used for QT are resource intensive and scale poorly with system size. Even for modest sized Hilbert spaces corresponding to only a few qubits, this puts a premium on schemes that are as efficient as possible. Theoretical work on QST has identified sets of POVM elements that are optimal under varying assumptions, in each case prescribing a minimal number of measurements of a given structure. Laboratory exploration of these POVM constructions has, however, been constrained by the ability to control SPAM errors and generate accurate test states and processes in all but the simplest quantum systems. Here we present the findings from a comprehensive experimental study comparing 6 different POVM constructions and 4 different state estimators, using as our testbed the d = 16 dimensional hyperfine manifold in the 6S1/2 electronic ground state of the 133Cs atom. Our results show a clear trade-off between efficiency and robustness to experimental error, with mutually unbiased bases achieving the best compromise in our system and reaching a QST fidelity of ~98% in d = 16. We have further used a minimal set of intelligently chosen probe states to implement QPT, testing the scheme on randomly chosen unitary processes in Hilbert spaces of varying dimension, and reaching a QPT fidelity of ~90% in d = 16.

4:45 pm - 5:15 pm Laura De Lorenzo, Schwab group (IQIM, Caltech)
Exploring the macroscopic quantum physics of motion with superfluid He-4

Abstract. We demonstrate the utility of superfluid helium-4 as an extremely low loss optomechanical element. We form an optomechanical system with a cylindrical niobium superconducting TE011 resonator whose 40 cm^3 inner cylindrical cavity is filled with He-4. Coupling is realized via the variations in permittivity resulting from the density profile of the acoustic modes. Acoustic losses in helium-4 below 500 mK are governed by the intrinsic nonlinearity of sound, leading to an attenuation which drops as T^4, indicating the possibility of quality factors (Q) over 10^10 at 10 mK. In our lowest loss mode, we demonstrate this T^4 law at temperatures down to 50 mK, realizing an acoustic Q of 1.35*10^8 at 8.1 kHz. When coupled with a low phase noise microwave source, we expect this system to be utilized as a probe of macroscopic quantized motion, for precision measurements to search for fundamental physical length scales, and as a continuous gravitational wave detector. Our estimates suggest that a resonant superfluid acoustic system could exceed the sensitivity of current broad-band detectors for narrow-band sources such as pulsars.

SQuInT Chief Organizer
Prof. Akimasa Miyake
amiyake@unm.edu

SQuInT Co-Organizer
Prof. Elohim Becerra
fbecerra@unm.edu

SQuInT Founder
Prof. Ivan Deutsch
ideutsch@unm.edu

SQuInT Administrator
Gloria Cordova
gjcordo1@unm.edu
505 277-1850

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