A5084665244- Quantum Information and Cryptography
- Quantum Mechanics and Applications
- Quantum Computing Algorithms and Architecture
- Neural Networks and Reservoir Computing
- Quantum optics and atomic interactions
- Optical Network Technologies
- Quantum many-body systems
- Statistical Mechanics and Entropy
- Photonic and Optical Devices
- Quantum and electron transport phenomena
- Blind Source Separation Techniques
- Quantum Mechanics and Non-Hermitian Physics
- Cellular Automata and Applications
- Coding theory and cryptography
Xanadu Quantum Technologies (Canada)
2018-2021
Université Libre de Bruxelles
2017-2018
Universitat Autònoma de Barcelona
2015-2017
Institute of Mathematical Sciences
2011
Photonics is the platform of choice to build a modular, easy-to-network quantum computer operating at room temperature. However, no concrete architecture has been presented so far that exploits both advantages qubits encoded into states light and modern tools for their generation. Here we propose such design scalable fault-tolerant photonic informed by latest developments in theory technology. Central our generation manipulation three-dimensional resource comprising bosonic squeezed vacuum...
Encoding a qubit in the continuous degrees of freedom an oscillator is promising path to error-corrected quantum computation. One advantageous way achieve this through Gottesman-Kitaev-Preskill (GKP) grid states, whose symmetries allow for correction any small error on oscillator. Unfortunately, ideal states have infinite energy, so it important find finite-energy approximations that are realistic, practical, and useful applications. In first half work we investigate impact imperfect GKP...
Generation of high fidelity photonic non-Gaussian states is a crucial ingredient for universal quantum computation using continous-variable platforms, yet it remains challenge to do so efficiently. We present general framework probabilistic production multimode by measuring few modes Gaussian via photon-number-resolving detectors. use elements consisting squeezed displaced vacuum and interferometers, the only derive analytic expressions output Wigner function, probability generating in terms...
Operator-sum or Kraus representations for single-mode bosonic Gaussian channels are developed, and several of their consequences explored. The fact that the two-mode metaplectic operators acting as unitary purification these do not, in canonical form, mix position momentum variables is exploited to present a procedure which applies uniformly all families Holevo classification. In this every quantum-limited channel can be simply read off from matrix elements corresponding operator. employed...
We consider conditional photonic non-Gaussian state preparation using multimode Gaussian states and photon-number-resolving detectors in the presence of photon loss. While simulation such is often computationally challenging, we show that obtaining required Fock matrix elements can be reduced to computation functions known as loop hafnians develop a tailored algorithm for their calculation faster than previously methods. As an example its utility, use our explore loss parameter space three...
The scalability of photonic implementations fault-tolerant quantum computing based on Gottesman-Kitaev-Preskill (GKP) qubits is injured by the requirements inline squeezing and reconfigurability linear optical network. In this work we propose a topologically error-corrected architecture that does away with these elements at no cost - in fact, an advantage to state preparation overheads. Our computer consists three modules: 2D array probabilistic sources GKP states; depth-four circuit static...
We introduce photonic architectures for universal quantum computation. The first step is to produce a resource state which superposition of the four Fock states with probability greater than or equal ${10}^{\ensuremath{-}2}$, an increase by factor ${10}^{4}$ over standard sequential photon-subtraction techniques. produced near-perfect fidelity from gadget that uses displaced squeezed vacuum states, interferometers, and photon-number-resolving detectors. parameters this are trained using...
The recently developed Kraus representation for bosonic Gaussian channels is employed to study analytically the robustness of non-Gaussian entanglement against evolution under noisy attenuator and amplifier environments, compare it with entanglement. Our results show that some states one ebit are more robust than all states, even ones arbitrarily large entanglement, a conclusion direct consequence recent conjecture by Allegra et al. [PRL, 105, 100503 (2010)].
We present a framework for studying bosonic non-Gaussian channels of continuous-variable systems. Our emphasis is on class that we call photon-added Gaussian channels, which are experimentally viable with current quantum-optical technologies. A strong motivation considering these the fact it compulsory to go beyond domain numerous tasks in quantum information processing such as entanglement distillation from states and universal computation. The single-mode consider obtained by using...
Universal quantum computation using photonic systems requires gates the Hamiltonians of which are order greater than quadratic in quadrature operators. We first review previous proposals to implement such gates, where specific non-Gaussian states used as resources conjunction with entangling continuous-variable versions controlled-phase and controlled-not gates. then propose ON superpositions vacuum $N\mathrm{th}$ Fock state, for use resource states. show that can be cubic higher-order phase...
Bosonic qubits are a promising route to building fault-tolerant quantum computers on variety of physical platforms. Studying the performance bosonic under realistic gates and measurements is challenging with existing analytical numerical tools. We present novel formalism for simulating classes states that can be represented as linear combinations Gaussian functions in phase space. This allows us analyze simulate wide class non-Gaussian states, transformations, measurements. demonstrate how...
We introduce a quantum-optical notion of nonclassicality that we call the process output for multimode quantum channels. The motivation comes from an information-theoretic point view and emphasis is on states channel. deem channel to be ``classical'' if its outputs are always classical irrespective input, i.e., breaking, nonclassical otherwise. Our condition stronger than one considered by Rahimi-Keshari et al., [Phys. Rev. Lett. 110, 160401 (2013)] compare two approaches. Using our...
Nonclassicality and entanglement are notions fundamental to quantum-information processes involving continuous variable systems. That these two intimately related has been intuitively appreciated for quite some time. An aspect of considerable interest is the behavior attributes a state under action noisy channel. Inspired by notion entanglement-breaking channels, we define concept nonclassicality-breaking channels in natural manner. We show that nonclassicality breaking essentially...
We compare two sets of multimode quantum channels acting on a finite collection harmonic oscillators: (a) the set linear bosonic channels, whose action is described as transformation at phase space level; and (b) Gaussian dilatable that admit Stinespring dilation involving unitary. Our main result coincides with closure respect to strong operator topology. also present an example channel in which not (b), implying taking general necessary. This provides complete resolution conjecture posed...
Implementing quantum algorithms is essential for computation. We study the implementation of three on a two-dimensional temporal continuous-variable cluster state. first review generation states and gates using measurement-based model. Alongside this we discuss methods to introduce non-Gaussianity into states. The algorithm consider Gaussian boson sampling in which only unitaries need be implemented. Taking account fact that input are also Gaussian, errors due effect finite squeezing can...
The Glauber-Sudarshan diagonal `weight' function provides a natural divide between the quantum-optical notion of classical and nonclassical states continuous variables systems. Based on this demarcation, channel is said to be nonclassicality breaking if it outputs only for any input state. We focus multimode bosonic Gaussian channels classify those that are by introducing criterion needs satisfied matrices representing these channels. can interpreted as benchmark since quantifies threshold...
We present a detailed analytic framework for studying multimode non-Gaussian states that are conditionally generated when few modes of Gaussian state subject to photon-number-resolving detectors. From the output Wigner function, we deduce factorizes into gate applied finite Fock-superposition state. The provides an approach find optimal strategy generate given target explore examples, such as generation cat states, weak cubic phase and bosonic code achieve improvements success probability...
The traditional scheme for realizing open-system quantum dynamics takes the initial state of system-bath composite as a simple product. Currently, however, issue correlations possibly affecting reduced system has been attracting considerable interest. influential work Shabani and Lidar [PRL {\bf 102}, 100402 (2009)] famously related this to discord, concept which in recent years occupied centre-stage information theory led several fundamental results. They suggested that is completely...
We present a general framework and procedure to derive uncertainty relations for observables of quantum systems in covariant manner. All such are consequences the positive semidefiniteness density matrix state. Particular emphasis is given action unitary symmetry operations system on chosen observables, covariance under these operations. The method applied case an $n$-mode recover $Sp(2n,\,R)$-covariant multi mode generalization single Schrödinger-Robertson Uncertainty Principle; set all...
We show that the positivity of Wigner function Gaussian states and measurements provides an elegant way to bound discriminating power "linear optics", which we formalise as measurement operations augmented by classical (feed-forward) communication (GOCC). This allows us reproduce generalise result Takeoka Sasaki [PRA 78:022320, 2008], tightly characterises GOCC norm distance coherent states, separating it from optimal distinguishability according Helstrom's theorem. Furthermore, invoking...
Classical correlation and quantum discord are computed for two-qubit $X$-states. Our approach, which is inspired by the methods of classical polarization optics, geometric in sense that entire analysis tied to ellipsoid all normalized conditional states A-qubit with measurement elements applied B-qubit. Aspects computation depend on location reduced state A inside get clearly separated from those do not. treatment comprehensive\,: known results reproduced, often more economically, several...
Continuous-variable systems in quantum theory can be fully described through any one of the $s$-ordered family quasiprobabilities ${\mathrm{\ensuremath{\Lambda}}}_{s}(\ensuremath{\alpha}), s\ensuremath{\in}[\ensuremath{-}1,1]$. We ask for what values $(s,a)$ is scaling map ${\mathrm{\ensuremath{\Lambda}}}_{s}(\ensuremath{\alpha})\ensuremath{\rightarrow}{a}^{\ensuremath{-}2}{\mathrm{\ensuremath{\Lambda}}}_{s}({a}^{\ensuremath{-}1}\ensuremath{\alpha})$ a positive map? Our analysis based on...