T. Coudreau
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View article: Implementable hybrid entanglement witness
Implementable hybrid entanglement witness Open
Hybrid encoding of quantum information is a promising approach towards the\nrealisation of optical quantum protocols. It combines advantages of continuous\nvariables encoding, such as high efficiencies, with those of discrete\nvariables, s…
View article: Producing a delocalized frequency-time Schrödinger-cat-like state with Hong-Ou-Mandel interferometry
Producing a delocalized frequency-time Schrödinger-cat-like state with Hong-Ou-Mandel interferometry Open
In the late 80's, Ou and Mandel experimentally observed signal beatings by\nperforming a non-time resolved coincidence detection of two photons having\ninterfered in a balanced beam splitter [Phys. Rev. Lett 61, 54 (1988)]. In this\nwork, …
View article: Generation of a time-frequency grid state with integrated biphoton frequency combs
Generation of a time-frequency grid state with integrated biphoton frequency combs Open
Encoding quantum information in continuous variables is intrinsically faulty. Nevertheless, redundant qubits can be used for error correction, as proposed by Gottesman, Kitaev and Preskill in Phys. Rev. A \textbf{64} 012310, (2001). We sho…
View article: Metrological advantage at finite temperature for Gaussian phase estimation
Metrological advantage at finite temperature for Gaussian phase estimation Open
In the context of phase estimation with Gaussian states, we introduce a quantifiable definition of metrological advantage that takes into account thermal noise in the preparation procedure. For a broad set of states, \textit{isotropic non-…
View article: Continuous variables error correction with integrated biphoton frequency combs
Continuous variables error correction with integrated biphoton frequency combs Open
Encoding quantum information in continuous variables is intrinsically faulty. Nevertheless, redundant qubits can be used for error correction, as proposed by Gottesman, Kitaev and Preskill in Phys. Rev. A \textbf{64} 012310, (2001). We sho…
View article: Demonstration of an Effective Ultrastrong Coupling between Two Oscillators
Demonstration of an Effective Ultrastrong Coupling between Two Oscillators Open
When the coupling rate between two quantum systems becomes as large as their characteristic frequencies, it induces dramatic effects on their dynamics and even on the nature of their ground state. The case of a qubit coupled to a harmonic …
View article: Connecting measurement invasiveness to optimal metrological scenarios
Connecting measurement invasiveness to optimal metrological scenarios Open
The connection between the Leggett-Garg inequality and optimal scenarios from the point of view of quantum metrology is investigated for perfect and noisy general dichotomic measurements. In this context, we show that the Fisher informatio…
View article: Superradiant phase transition in the ultrastrong-coupling regime of the two-photon Dicke model
Superradiant phase transition in the ultrastrong-coupling regime of the two-photon Dicke model Open
The controllability of current quantum technologies allows to implement\nspin-boson models where two-photon couplings are the dominating terms of\nlight-matter interaction. In this case, when the coupling strength becomes\ncomparable with …
View article: Quantum simulation of ultrastrongly coupled bosonic modes using superconducting circuits
Quantum simulation of ultrastrongly coupled bosonic modes using superconducting circuits Open
The ground state of a pair of ultrastrongly coupled bosonic modes is predicted to be a two-mode squeezed vacuum. However, the corresponding quantum correlations are currently unobservable in condensed matter where such a coupling can be re…
View article: General conditions for maximal violation of non-contextuality in discrete and continuous variables
General conditions for maximal violation of non-contextuality in discrete and continuous variables Open
The contextuality of quantum mechanics, i.e. the measurement outcome\ndependence upon previously made measurements, can be shown by the violation of\ninequalities based on measurements of well chosen observables. An important\nproperty of …
View article: Continuous-Variable Instantaneous Quantum Computing is Hard to Sample
Continuous-Variable Instantaneous Quantum Computing is Hard to Sample Open
Instantaneous quantum computing is a subuniversal quantum complexity class, whose circuits have proven to be hard to simulate classically in the discrete-variable realm. We extend this proof to the continuous-variable (CV) domain by using …
View article: Quantum communication between remote mechanical resonators
Quantum communication between remote mechanical resonators Open
Mechanical resonators represent one of the most promising candidates to\nmediate the interaction between different quantum technologies, bridging the\ngap between efficient quantum computation and long-distance quantum\ncommunication. In t…
View article: Generalized spin-squeezing inequalities for particle number with quantum fluctuations
Generalized spin-squeezing inequalities for particle number with quantum fluctuations Open
Particle number fluctuations, no matter how small, are present in\nexperimental set-ups. One should rigorously take these fluctuations into\naccount, especially, for entanglement detection. In this context, we generalize\nthe spin squeezin…
View article: Quantum information processing in phase space: A modular variables approach
Quantum information processing in phase space: A modular variables approach Open
Binary quantum information can be fault tolerantly encoded in states defined in infinite dimensional Hilbert spaces. Such states define a computational basis, and permit a perfect equivalence between continuous and discrete universal opera…
View article: Output squeezed radiation from dispersive ultrastrong light-matter coupling
Output squeezed radiation from dispersive ultrastrong light-matter coupling Open
We investigate the output generation of squeezed radiation of a cavity photon mode coupled to another off-resonant bosonic excitation. By modulating in time their linear interaction, we predict high degree of output squeezing when the disp…
View article: Contextually in a Peres—Mermin square using arbitrary operators
Contextually in a Peres—Mermin square using arbitrary operators Open
The contextuality of quantum mechanics can be shown by the violation of inequalities based on measurements of well chosen observables. These inequalities have been designed separately for both discrete and continuous variables. Here we uni…
View article: About what can be witnessed by a Leggett—Garg inequality test: modeling its violation
About what can be witnessed by a Leggett—Garg inequality test: modeling its violation Open
The Leggett-Garg inequality is a widely used test of the "quantumness" of a system, and involves correlations between measurements realized at different times. According to its widespread interpretation, a violation of the Legget-Garg ineq…
View article: Modeling Leggett-Garg-inequality violation
Modeling Leggett-Garg-inequality violation Open
The Leggett-Garg inequality is a widely used test of the "quantumness" of a\nsystem, and involves correlations between measurements realized at different\ntimes. According to its widespread interpretation, a violation of the\nLegget-Garg i…
View article: Demonstrating the contextuality of quantum mechanics with observables in Hilbert spaces of arbitrary dimensions
Demonstrating the contextuality of quantum mechanics with observables in Hilbert spaces of arbitrary dimensions Open
The contextuality of quantum mechanics can be shown by the violation of inequalities based on measurements of well chosen observables. An important property of such observables is that their expectation value can be expressed in terms of p…
View article: General dichotomization procedure to provide qudit entanglement criteria
General dichotomization procedure to provide qudit entanglement criteria Open
We present a general strategy to derive entanglement criteria which consists in performing a mapping from qudits to qubits that preserves the separability of the parties and SU(2) rotational invariance. Consequently, it is possible to appl…
View article: Toolbox for continuous-variable entanglement production and measurement using spontaneous parametric down-conversion
Toolbox for continuous-variable entanglement production and measurement using spontaneous parametric down-conversion Open
We provide a toolbox for continuous variables quantum state engineering and characterization of biphoton states produced by spontaneous parametric down conversion in a transverse pump configuration. We show that the control of the pump bea…
View article: Testing the Clauser-Horne-Shimony-Holt inequality using observables with arbitrary spectrum
Testing the Clauser-Horne-Shimony-Holt inequality using observables with arbitrary spectrum Open
The Clauser-Horne-Shimony and Holt inequality applies when measurements with binary outcomes are performed on physical systems under the assumption of local realism. Testing such inequalities in the quantum realm usually involves either me…