Session Overview |
Tuesday, May 28 |
15:40 |
Rotational Control of Molecules and Rotons in Superfluid Helium
* V. Milner, University of British Columbia, Canada A. A. Milner, University of British Columbia, Canada P. C. E. Stamp, University of British Columbia, Canada I. MacPhail-Bartley, University of British Columbia, Canada K. Preocanin, University of British Columbia, Canada S. Dasgupta, University of British Columbia, Canada X. Peng, University of British Columbia, Canada Molecules immersed in liquid helium are excellent probes of superfluidity. Their electronic, vibrational and rotational dynamics provide valuable clues about the superfluid at the nanoscale. We present an experimental study of the laser-induced rotation of helium dimers inside the superfluid 4He bath at variable temperature. The coherent rotational dynamics of He2 is initiated in a controlled way by ultrashort laser pulses, and tracked by means of time-resolved laser-induced fluorescence. We detect the decay of rotational coherence on the nanosecond timescale and investigate the effects of temperature on the decoherence rate. The observed temperature dependence suggests a non-equilibrium evolution of the quantum bath, accompanied by the emission of the wave of second sound. The method offers new ways of studying superfluidity with molecular nano-probes under variable thermodynamic conditions. A Superfluid 4He is a very dense system of strongly interacting quasiparticles (phonons, maxons and rotons), which determine the fascinating properties of this quantum liquid. Quasiparticle properties are deduced from experiment, predominantly with neutron scattering, and controversies over their description still remain, notably regarding the nature of rotons and their binding into roton pairs. We developed a method of studying roton pairs in superfluid helium after exciting them with either a femtosecond laser pulse or a shaped pulse known as an optical centrifuge. By tracking the non-equilibrium dynamics of the laser-induced two-roton states on a picosecond timescale, we observe an ultrafast cooling of hot roton pairs as they thermalize with the colder gas of other quasiparticles. We show that the thermalization rate increases with increasing temperature of the helium bath, with no detectable dynamics above the superfluid transition. We also demonstrate that the angular momentum of the roton pair can be controlled with an optical centrifuge. |
16:05 |
Quantum Sensing with Diamond Defects
* Erika Janitz, University of Calgary, Canada The electronic spins of single atomic defects in diamond can serve as magnetic sensors with exceptional sensitivity and nanoscale spatial resolution. So far, the nitrogen-vacancy (NV) center has been used for sensing external targets, partly due to its exceptional spin coherence under various experimental (including ambient) conditions. In this talk, I will discuss my postdoctoral work (Degen group; ETH Zurich) in creating an NV-NMR platform for molecular sensing. Our team developed fabrication and surface treatments for improving sensitivity while enabling highly generalizable molecular surface functionalization [1]. These techniques were subsequently used to detect conformational changes in few-molecule DNA samples. In parallel, we developed optimized diamond nanopillar structures for improving NV fluorescence collection, yielding a factor-of-three measurement speed-up [2]. I will conclude by outlining plans for my new lab to improve magnetic sensitivity further, enabling single-nuclear-spin detection within functionalized molecules and opening the door for structure elucidation or reaction monitoring on the single-molecule level. [1] Abendroth et al., Nano Letters 22, (2022). [2] Zhu et al., Nano Letters 23, (2023). |
16:30 |
Observation of a group delay in high-gain parametric down-conversion
* Guillaume Thekkadath, National Research Council Canada, Canada Martin Houde, École Polytechnique de Montréal Duncan England, National Research Council Canada Nicolás Quesada, École Polytechnique de Montréal Ben Sussman, National Research Council Canada We experimentally observed a gain-dependent group delay between photon pairs produced in type-II parametric down-conversion. The group delay can be explained by considering higher order terms in the time-ordered perturbative expansion of the nonlinear Hamiltonian interaction. |
16:55 |
Phase Retrieval of Spatial Bi-photon States from Coincidence Images
* Nazanin Dehghan, University of Ottawa, Canada Alessio D'Errico, University of Ottawa, Canada Francesco Di Colandrea, University of Ottawa, Canada Danilo Zia, Sapienza Universita, Italy Fabio Sciarrino, Sapienza Universita, Italy Ebrahim Karimi, University of Ottawa, Canada The full measurement of the quantum state of two correlated photons requires reconstructing the amplitude and phase of the bi-photon wave function. This task is commonly performed via projective measurements. Recently, time stamping cameras allowed for the implementation of classically inspired methods, such as digital holography, and various phase retrieval algorithms. |
17:10 |
A new light on correlations for multimode states
* Aaron Goldberg, National Research Council of Canada, Canada We present a new formalism for old intuition: the nth-order correlations in a multimode state are equivalent to the density matrix elements of the state formed by choosing n photons “at random” from the overall state and ignoring the rest. We develop expressions for choosing photons at random from a state. One photon randomly chosen will encode the state’s intensity phenomena (like polarization), two will encode auto- and cross-correlation functions, and so on; this construction is unique and comprehensive. |
17:25 |
Free-Space Spin-Preserving Chiral Cavities
* Behrooz Semnani, University of Waterloo, Canada Mohammad Soltani, University of Waterloo, Canada Anna Maria Houk, University of Waterloo Sai Sreesh Venuturumilli, University of Waterloo Michal Bajcsy, University of Waterloo, Canada We present experimental evidence of chiral resonant modes in a Fabry-Perot cavity with spin preservation using geometric-phase reflective metasurfaces. The cavity stabilizes a specific spin of light and preserves helicity during round propagation. |
17:40 |
Optical memory and spectroscopy of 171Yb3+: Y2SiO5 at millikelvin temperatures
* Nasser Gohari Kamel, Department of Physics and Astronomy and Institute for Quantum Science and Technology, University of Calgary, Canada Farhad Rasekh, Department of Physics and Astronomy and Institute for Quantum Science and Technology, University of Calgary, Canada Ujjwal Gautam, Department of Physics and Astronomy and Institute for Quantum Science and Technology, University of Calgary, Canada Sourabh Kumar, Department of Physics and Astronomy and Institute for Quantum Science and Technology, University of Calgary, Canada Vahid Salari, Department of Physics and Astronomy and Institute for Quantum Science and Technology, University of Calgary, Canada Erhan Saglamyurek, Lawrence Berkeley National Laboratory and Department of Physics, University of California, Berkeley, United States of America Daniel Oblak, Department of Physics and Astronomy and Institute for Quantum Science and Technology, University of Calgary, Canada In this study we explore the spectroscopic properties of 171Yb3+ ions doped into Y2SiO5 at zero magnetic field and implement optical memory. The coherence time extends from 200 μs at 4 K to 600 μs at 10 mK, with spin relaxation times surpassing 200 minutes at 10 mK. Leveraging the prolonged coherence time, we successfully implemented the Atomic Frequency Comb (AFC) quantum memory protocol, achieving a storage duration of up to 200 μs of an optical input pulse. |