A5017203711- Quantum Information and Cryptography
- Quantum Computing Algorithms and Architecture
- Quantum Mechanics and Applications
- Quantum optics and atomic interactions
- Cold Atom Physics and Bose-Einstein Condensates
- Quantum and electron transport phenomena
- Neural Networks and Reservoir Computing
- Mechanical and Optical Resonators
- Photonic and Optical Devices
- Laser-Matter Interactions and Applications
- Atomic and Subatomic Physics Research
- Quantum-Dot Cellular Automata
- Quantum many-body systems
- Photonic Crystals and Applications
- Advanced Fiber Laser Technologies
- Topological Materials and Phenomena
- Advanced Antenna and Metasurface Technologies
- Plasmonic and Surface Plasmon Research
- Spectroscopy and Quantum Chemical Studies
- Quantum chaos and dynamical systems
- Orbital Angular Momentum in Optics
- Microwave Engineering and Waveguides
- Semiconductor Quantum Structures and Devices
- Strong Light-Matter Interactions
- Antenna Design and Analysis
University of Calgary
2016-2025
CAS Key Laboratory of Urban Pollutant Conversion
2016-2023
University of Science and Technology of China
2014-2023
Hefei National Center for Physical Sciences at Nanoscale
2014-2023
Canadian Institute for Advanced Research
2014-2023
Beijing Academy of Quantum Information Sciences
2023
Raman Research Institute
2019-2023
Lakehead University
2022
University of Hong Kong
2022
Fuzhou University
2022
We provide limits to practical quantum key distribution, taking into account channel losses, a realistic detection process, and imperfections in the "qubits" sent from sender receiver. As we show, even distribution with perfect qubits might not be achievable over long distances when other are taken account. Furthermore, existing experimental schemes (based on weak pulses) currently do offer unconditional security for reported signal strength. Finally show that parametric down-conversion...
We demonstrate a multipartite protocol to securely distribute and reconstruct quantum state. A secret state is encoded into tripartite entangled distributed three players. Any two of the players are able state, whilst individual obtain nothing. characterize this (2,3) threshold sharing scheme in terms fidelity, signal transfer reconstruction noise. fidelity averaged over all permutations 0.73, which achievable only using resources.
The nonlinear Mach-Zehnder interferometer is presented as a device whereby pair of coherent states can be transformed into an entangled superposition for which the notion entanglement generalized to include nonorthogonal, but distinct, component states. Each mode directed homodyne detector. We show that there exist nonclassical intensity correlations at output ports detectors facilitate test local realism. In contradistinction previous optical schemes realism, initial state used here...
Photon-mediated interactions between atoms are of fundamental importance in quantum optics, simulations, and information processing. The exchange real virtual photons gives rise to nontrivial interactions, the strength which decreases rapidly with distance three dimensions. Here, we use two superconducting qubits an open one-dimensional transmission line study much stronger photon-mediated interactions. Making possibility tune these by more than a quarter their transition frequency, observe...
We consider three broad classes of quantum secret sharing with and without eavesdropping show how a graph state formalism unifies otherwise disparate models. In addition to the elegant unification provided by states, our approach provides generalization threshold classical via insecure channels beyond current requirement 100% collaboration players just simple majority in case five players. Another innovation here is introduction embedded protocols within larger that serves as one-way...
We obtain sufficient conditions for the efficient simulation of a continuous variable quantum algorithm or process on classical computer. The resulting theorem is an extension Gottesman-Knill to information. For collection harmonic oscillators, any that begins with unentangled Gaussian states, performs only transformations generated by Hamiltonians are quadratic in canonical operators, and involves measurements operators (including finite losses) suitable operations conditioned these can be...
Qudit is a multi-level computational unit alternative to the conventional 2-level qubit. Compared qubit, qudit provides larger state space store and process information, thus can provide reduction of circuit complexity, simplification experimental setup enhancement algorithm efficiency. This review an overview qudit-based quantum computing covering variety topics ranging from building, design, methods. We first discuss gate universality gates including pi/8 gate, SWAP multi-level-controlled...
Autler-Townes splitting (ATS) and electromagnetically induced transparency (EIT) both yield in an absorption profile, but only EIT yields strong for a weak pump field due to Fano interference. Empirically discriminating from ATS is important so far has been subjective. We introduce objective method, based on Akaike's information criterion, test vs experimental data three-level atomic systems determine which pertains. apply our method recently reported induced-transparency experiment...
We study the collective effects that emerge in waveguide quantum electrodynamics where several (artificial) atoms are coupled to a one-dimensional superconducting transmission line. Since single microwave photons can travel without loss for long distance along line, real and virtual emitted by one atom be reabsorbed or scattered second atom. Depending on between atoms, this effect lead super- subradiance coherent exchange-type interaction atoms. Changing artificial transition frequencies,...
We review entangled coherent state research since its first implicit use in 1967 to the present. Entangled states are important quantum superselection principles, information processing, optics, and mathematical physics. Despite their inherent fragility they have produced a conditional propagating-wave optics realization. Fundamentally intriguing because entanglements of states, which sense most classical all dynamical system.
We report the experimental detection of bulk topological invariants in nonunitary discrete-time quantum walks with single photons. The nonunitarity dynamics is enforced by periodically performing partial measurements on polarization walker photon, which effectively introduces loss to dynamics. invariant walk manifested quantized average displacement walker, probed monitoring photon loss. confirm properties system observing localized edge states at boundary regions different invariants....
We analyse the quantum walk in higher spatial dimensions and compare classical spreading as a function of time. Tensor products Hadamard transformations discrete Fourier transform arise natural extensions 'quantum coin toss' one-dimensional simulation, other illustrative are also investigated. find that entanglement between serves to reduce rate spread walk. The limit is obtained by introducing random phase variable.
We prove that it is possible to remotely prepare an ensemble of noncommuting mixed states using communication equal the Holevo information for this ensemble. This remote preparation scheme may be used convert between different ensembles in asymptotically lossless way, analogous concentration and dilution entanglement.
Quantum information theory is applied to practical interferometer-based phase measurements deduce the optimal measurement scheme with two optical modes. Optimal measurements, given ideal input states, reveal an asymptotic $1/n$ decrease in uncertainty $\ensuremath{\Delta}\ensuremath{\theta}$ for $n$ mean photon number of state. In contradistinction previous schemes realizing number-phase limit, limit achieved here independent interferometer shift; prior about expected shift not necessary...
We show that spin squeezing implies pairwise entanglement for arbitrary symmetric multiqubit states. If the parameter is less than or equal to 1, we demonstrate a quantitative relation between and concurrence even odd prove states generated from initial state with all qubits being down, via one-axis twisting Hamiltonian, are squeezed if only they entangled. For Hamiltonian an external transverse field any number of greater 1 two-axis countertwisting qubits, numerical results suggest such
A resonator antenna made from a complex artificial surface and metallic ground plane is described. The realized using woodpile electromagnetic bandgap (EBG) material, which shown to have frequency dependent reflection location. highly directive radiation pattern created due the angle-dependent attenuation of coupling free space. has advantages low height, loss, sidelobes. It that directivity can be varied over fixed range by changing aperture size device, with maximum determined both feed...
We present a decomposition scheme based on Lie–Trotter–Suzuki product formulae to approximate an ordered operator exponential with of ordinary exponentials. show, using counterexample, that approximations may be lower order than expected when applied problems have singularities or discontinuous derivatives appropriate order. To address this problem, we set criteria is sufficient for the validity these approximations, prove convergence and provide upper bounds approximation error. This work...
We propose replacing concurrence by convex-roof extended negativity (CREN) for studying monogamy of entanglement (MOE). show that all proven MOE relations using can be rephrased in terms CREN. Furthermore, we higher-dimensional (qudit) extensions CREN are not disproven any the counterexamples used to disprove qudit concurrence. further test version qudits considering fully or partially coherent mixtures a $W$-class state with vacuum and is satisfied this case as well. The thus strong...
Adaptive feedback schemes are promising for quantum-enhanced measurements yet complicated to design. Machine learning can autonomously generate algorithms in a classical setting. Here we adapt machine quantum information and use our framework autonomous adaptive measurement. In particular, approach replaces guesswork measurement by logical, fully automatic, programable routine. We show that method yields outperform the best known scheme interferometric phase estimation.
The quantum and classical dynamics of the nonlinear oscillator are contrasted by comparing evolution Q function with that a similar probability distribution. rotator is shown to generate superposition two distinct coherent states from coherent-state input. Measurements angular-momentum components signature state discussed. effects continual measurement one component introduced into model, its on coherences degrade coherence effects. We present optical model obeys can superpositions SU(2)...
The adiabatic theorem states that an initial eigenstate of a slowly varying Hamiltonian remains close to instantaneous the at later time. We show perfunctory application this statement is problematic if change in significant, regardless how closely evolution satisfies requirements theorem. also introduce example two-level system with exactly solvable demonstrate inapplicability approximation for particular Hamiltonian.