# Claude FabreSorbonne Université | UPMC · Laboratoire Kastler-Brossel (LKB)

Claude Fabre

Professor

## About

430

Publications

25,998

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11,981

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Introduction

Theoretical and experimental work on quantum correlations, entanglement and fluctuations in light mainly in parametric devices.
Quantum effects in highly multimode systems, such as optical images and trains of ultrashort light pulses. Applications to quantum information processing.
Characterization of quantum properties of optical detectors. Minimization of quantum limits in high sensitivity optical measurements Ultra-accurate space-time positioning beyond the standard quantum limit.

Additional affiliations

October 1996 - present

September 1974 - September 1996

September 1970 - September 1974

## Publications

Publications (430)

We determine the ultimate quantum limits on the estimation of a "mode parameter" that modifies the spatiotemporal structure of the modes occupied by a parameter-independent quantum state. Our analytical expression for the quantum Cram\'{e}r-Rao bound for arbitrary multimode states, pure or mixed, Gaussian or non-Gaussian, reveals the origin of quan...

Measuring the spectral properties of an optical frequency comb is among the most fundamental tasks of precision metrology. In contrast to general single-parameter measurement schemes, we demonstrate here single shot multi-parameter estimation of an optical frequency comb at and beyond the standard quantum limit. The mean energy and the central freq...

Quantum key distribution with continuous variables already uses advantageous high-speed single-mode homodyne detection with low electronic noise at room temperature. Together with continuous-variable information encoding to nonclassical states, the distance for secure key transmission through lossy channels can approach 300 km in current optical fi...

Le père jésuite Ignace Gaston Pardies, outre son activité d’enseignant dans les collèges jésuites comme celui de Clermont à Paris, a été au coeur des débats concernant la nature de la lumière, correspondant avec Newton, Leibniz, Huygens et bien d’autres savants européens. Avant Huygens, il a été le premier à proposer une théorie détaillée et argume...

Léon Brillouin a été durant toute sa carrière au coeur des développements de la nouvelle physique quantique. Il lui a apporté des contributions majeures et originales, notamment en physique du solide. Il a participé à l’émergence d’une nouvelle discipline scientifique : l’informatique.

In 1935, Schrödinger introduced the word "entanglement" to describe a situation examined in the famous Einstein-Podolsky-Rosen paper published a few months before. The proper nature of quantum correlations that exist when a two-partite system is in an entangled state was a subject of controversy. In contrast to many other subjects, the debate about...

We theoretically investigate the generation of two entangled beams of light in the process of single-pass type-I noncollinear frequency-degenerate parametric down-conversion with an ultrashort pulsed pump. We find the spatiotemporal squeezing eigenmodes and the corresponding squeezing eigenvalues of the generated field both numerically and analytic...

We theoretically investigate the generation of two entangled beams of light in the process of single-pass type-I noncollinear frequency degenerate parametric downconversion with an ultrashort pulsed pump. We find the spatio-temporal squeezing eigenmodes and the corresponding squeezing eigenvalues of the generated field both numerically and analytic...

A few decades ago, quantum optics stood out as a new domain of physics by exhibiting states of light with no classical equivalent. The first investigations concerned single photons, squeezed states, twin beams, and Einstein-Podolsky-Rosen states, which involve only one or two modes of the electromagnetic field. The study of the properties of quantu...

Superresolution techniques based on intensity measurements after a spatial mode decomposition can overcome the precision of diffraction-limited direct imaging. However, realistic measurement devices always introduce finite crosstalk in any such mode decomposition. Here, we show that any nonzero crosstalk leads to a breakdown of superresolution when...

We have experimentally shown in a recent paper [Wang et al., Phys. Rev. A 95, 051802(R) (2017)] that a four-wave mixing (FWM) process in a Rb vapor with a spatially structured pump (SSP), consisting of a coherent combination of two tilted pump beams, can generate six well-separated bright beams that are quantum correlated. The experimental setup is...

We present the experimental implementation of simultaneous spatial multimode demultiplexing as a distance measurement tool. We first show a simple and intuitive derivation of the Fisher information in the presence of Poissonian noise. We then estimate the distance between two incoherent beams in both directions of the transverse plane, and find a p...

Irène Curie nait à Paris en 1897. Elle est la fille ainée de Pierre Curie et Marie Sklodowska-Curie. Une année auparavant, Henri Becquerel a découvert un rayonnement étrange émis par les sels d’uranium. Marie décide d’en faire le sujet de ses travaux de thèse, bientôt suivie par Pierre, qui laisse de côté ses recherches sur le magnétisme.

Superresolution techniques based on intensity measurements after a spatial mode decomposition can overcome the precision of diffraction-limited direct imaging. However, realistic measurement devices always introduce finite crosstalk in any such mode decomposition. Here, we show that any nonzero crosstalk leads to a breakdown of superresolution when...

Measuring the spectral properties of an optical frequency comb is among the most fundamental tasks of precision metrology. In contrast to general single-parameter measurement schemes, we demonstrate here single shot multiparameter estimation at and beyond the standard quantum limit. The mean energy and the central frequency of ultrafast pulses are...

We present a single-pass source of broadband multimode squeezed light with potential application in quantum information and quantum metrology. The source is based on a type I parametric down-conversion (PDC) process inside a bulk nonlinear crystal in a non-collinear configuration. The generated squeezed light exhibits a spatio-temporal multimode be...

Multipartite entanglement serves as a vital resource for quantum information processing. Generally, its generation requires complex beam splitting processes which limit scalability. A promising trend is to integrate multiple nonlinear processes into a single device via frequency or time multiplexing. The generated states in these schemes are useful...

Advanced quantum technologies require scalable and controllable quantum resources1,2. Gaussian states of multimode light, such as squeezed states and cluster states, are scalable quantum systems3,4,5, which can be generated on demand. However, non-Gaussian features are indispensable in many quantum protocols, especially to reach a quantum computati...

We present a single-pass source of broadband multimode squeezed light with potential application in quantum information and quantum metrology. The source is based on a type I parametric down-conversion (PDC) process inside a bulk nonlinear crystal in a non-collinear configuration. The generated squeezed light exhibits a spatiotemporal multimode beh...

A few decades ago, quantum optics stood out as a new domain of physics by exhibiting states of light with no classical equivalent. The first investigations concerned single photons, squeezed states, twin beams and EPR states, that involve only one or two modes of the electromagnetic field. The study of the properties of quantum light then evolved i...

We study noise propagation dynamics in a femtosecond oscillator by injecting external noise on the pump intensity. We utilize a spectrally resolved homodyne detection technique that enables simultaneous measurement of amplitude and phase quadrature noises of different spectral bands of the oscillator. We perform a modal analysis of the oscillator n...

We study the Bloch-Messiah reduction of parametric down-conversion of light in the pulsed regime with a nondegenerate phase matching providing generation of twin beams. We find that in this case every squeezing eigenvalue has multiplicity at least two. We discuss the problem of ambiguity in the definition of the squeezing eigenmodes in this case an...

We study noise propagation dynamics in a femtosecond oscillator by injecting external noise on the pump intensity. We utilize a spectrally-resolved homodyne detection technique that enables simultaneous measurement of amplitude and phase quadrature noises of different spectral bands of the oscillator. To reveal the impact of added pump noise on the...

We study the Bloch-Messiah reduction of parametric downconversion of light in the pulsed regime with a nondegenerate phase matching providing generation of twin beams. We find that in this case every squeezing eigenvalue has multiplicity at least two. We discuss the problem of ambiguity in the definition of the squeezing eigenmodes in this case and...

Even though Gaussian quantum states of multimode light are promising quantum resources due to their scalability, non-Gaussianity is indispensable for quantum technologies, in particular to reach quantum computational advantage. However, embodying non-Gaussianity in a multimode Gaussian state remains a challenge as controllable non-Gaussian operatio...

The experimental implementation of large multipartite entangled state in the time and frequency domain is realised via optical frequency comb and parametric process. We discuss the implementation of quantum complex networks and their non-Gaussian features

The first quantum-enhanced interferometric timing measurement with a squeezed optical frequency comb was demonstrated. The timing resolution at 2 MHz was improved from a shot-noise limited value of (2.8 ± 0.1) × 10−20 s to (2.4 ± 0.1) × 10−20 s.

We show the single-pass generation of entangled states featuring spatial-spectral quantum correlations via SPDC. They constitute multimode building blocks of dual-rail cluster states, which can be achieved via multiplexing in the time (pulsed) domain.

Accurate time-delay measurement has become a crucial issue for space positioning experiments which require increasing precision over large distances. The femtosecond frequency comb has been found to be a good source for its advantages of a large nonambiguity range and coherence length up to tens of kilometers or more. A scheme combining homodyne de...

Controlling the noise properties of optical frequency combs (OFC) is of great importance as most OFC-based precision measurements are limited by their intrinsic stability. It has been found that OFC noise manifests itself as fluctuations of only a few global parameters, which indicates strong correlations between the fluctuations of individual freq...

In this work, we investigate three different compact fibered systems generating vacuum squeezing that involve optical cavities limited by the end surface of a fiber and by a curved mirror and containing a thin parametric crystal. These systems have the advantage to couple squeezed states directly to a fiber, allowing the user to benefit from the fl...

We study the quantum correlations induced by spontaneous parametric down-conversion of a frequency comb. We derive a theoretical method to find the output state corresponding to a pump with an arbitrary spectral profile. After applying it to the relevant example of a spectrally chirped pump, we run an optimization algorithm to numerically find the...

Accurate time transfer has become a crucial issue for future space experiments which require increasing resolution over large distances. In 2008, a scheme combining homodyne detection and mode-locked femtosecond lasers was proposed that leads to a potential timing precision reaching the yoctosecond range; with a multimode quantum frequency comb as...

We present an upconversion imaging experiment from the near-infrared to the visible spectrum. Using a dedicated broadband pump laser to increase the number of resolved elements converted in the image we obtain up to 56x64 spatial elements with a 2.7 nm wide pump spectrum, more than 10 times the number of elements accessible with a narrowband laser....

We present an upconversion experiment designed for long range active imaging. Upconversion is a promising detection technique that allows us to benefit from all the performances of silicon based sensors to detect light above their maximum operating wavelength in an active imaging system. The detection sensitivity of such a system can be higher than...

We present a parametric down-conversion based source generating broadband squeezed light in multiple spectral modes. The source will be used to create large-scale cluster states, and to perform space-time positioning measurements beyond classical limit.

We study the quantum correlations induced by spontaneous parametric down-conversion of a frequency comb. We derive a theoretical method to find the output state corresponding to a pump with an arbitrary spectral profile. After applying it to the relevant example of a spectrally chirped pump, we run an optimization algorithm to numerically find the...

The addition or subtraction of a photon from a Gaussian state of light is a versatile and experimentally feasible procedure to create non-Gaussian states. In multimode setups, these states manifest a wide range of phenomena when the photon is added or subtracted in a mode-tunable way. In this contribution, we derive the truncated correlations, whic...

Non-Gaussian operations are essential to exploit the quantum advantages in optical continuous variable quantum information protocols. We focus on mode-selective photon addition and subtraction as experimentally promising processes to create multimode non-Gaussian states. Our approach is based on correlation functions, as is common in quantum statis...

Multimode entanglement is an essential resource for quantum information processing and quantum metrology. However, multimode entangled states are generally constructed by targeting a specific graph configuration. This yields to a fixed experimental setup that therefore exhibits reduced versatility and scalability. Here we demonstrate an optical on-...

Multimode quantum resources or states, in which quantum correlations are shared and distributed among multiple parties, are important not only for fundamental tests of quantum effects but also for their numerous possible applications in quantum technologies, such as quantum imaging and quantum metrology. Here we demonstrate the single-step fabricat...

We report an upconversion experiment using an orientation-patterned gallium arsenide (OP-GaAs) crystal to detect small mid-infrared signals on an InGaAs avalanche photodiode. A conversion efficiency up to 20% with a nonpolarized pulsed fiber pump is demonstrated. Our uncooled setup is favorably compared in terms of noise equivalent power, dynamic r...

An experimental scheme is introduced to measure multiple parameters that are encoded in the phase quadrature of a light beam. Using a modal description and a spectrally-resolved homodyne detection, it is shown that all of the information is collected simultaneously, such that a single measurement allows extracting the value of multiple parameters \...

Single-photon subtraction plays important roles in optical quantum information processing as it provides a non-Gaussian characteristic in continuous-variable quantum information. While the conventional way of implementing single-photon subtraction based on a low-reflectance beam splitter works properly for a single-mode quantum state, it is unsuita...

We investigate the impact of the spectral profile of the pump of a synchronously pumped optical parametric oscillator on the quantum properties of the output state, finding optimal shapes for producing approximate cluster states.

We present a new multimode squeezed-states quantum source operating in a single pass regime suitable for cluster states and complex network generation.

We implement a single-photon subtractor that can be tuned to subtract a single photon exclusively from one mode or coherently from multiple modes. We experimentally characterize the device by employing coherent-state quantum process tomography.

We implement a single-photon subtractor that can be tuned to subtract a single photon exclusively from one mode or coherently from multiple modes. We experimentally characterize the device by employing coherent-state quantum process tomography.

We consider a six-partite, continuous-variable quantum state that we have effectively generated by the parametric down-conversion of a femtosecond frequency comb. We show that, though this state is two-separable, i.e., it does not exhibit “genuine entanglement,” it is undoubtedly multipartite entangled. The consideration of not only the entanglemen...

We develop a general theory to describe the manipulation of a multimode quantum state of light via the subtraction of a single photon. The theory is applicable for various types of subtraction schemes independent of the physical nature of the light modes, their number or the embedded quantum states. We show that different subtraction schemes can be...

We present the quantum theory of the measurement of bosonic particles by multipixel detectors. For the sake of clarity, we specialize on beams of photons. We study the measurement of different spatial beam characteristics, as position and width. The limits of these measurements are set by the quantum nature of the light field. We investigate how bo...

In this work we introduce a general scheme for measurement based quantum computation in continuous variables. Our approach does not necessarily rely on the use of ancillary cluster states to achieve its aim, but rather on the detection of a resource state in a suitable mode basis followed by digital post-processing, and involves an optimization of...

Multimode entanglement is quintessential for the design and fabrication of quantum networks, which play a central role in quantum information processing and quantum metrology. However, an experimental setup is generally constructed with a specific network configuration in mind and therefore exhibits reduced versatility and scalability. The present...

This chapter describes the main results that have been recently obtained at the Laboratoire Kastler Brossel at the University Pierre Marie Curie in Paris concerning the quantum properties of optical frequency combs. The combs are generated by parametric down‐conversion and their use for quantum information processing. An alternative approach, calle...

Microscopy, wavefront correction, image processing, optical data storage, and optical measurements in general constitute a very important domain of our present‐day technologies. Optical technologies can directly benefit from the improvements brought by quantum effects and demonstrated by laboratory experiments, but their present complexity is an ob...

The existence of non-local quantum correlations is certainly the most important specific property of the quantum world. However, it is a challenging task to distinguish correlations of classical origin from genuine quantum correlations, especially when the system involves more than two parties, for which different partitions must be simultaneously...

For some crystalline materials, a regime can be found where continuous ductile cutting is feasible. Using precision diamond turning, such materials can be cut into complex optical components with high surface quality and form accuracy. In this work we use diamond-turning to machine a monolithic, square-shaped, doubly-resonant LiNbO 3 cavity with tw...

A methodology is introduced that enables an absolute, quantum-limited measurement of sub-wavelength interferometric displacements. The technique utilizes a high-frequency optical path modulation within an interferometer operated in a homodyne configuration. All of the information necessary to fully characterize the resultant path displacement is co...

!--StartFragment-->We describe a mode-selective single-photon subtraction device based on sum-frequency generation and ultrafast pulse shaping for multimode quantum state engineering. Its essential feature is the tunability of the single-photon subtraction mode.<!--EndFragment--

We theoretically investigate the quantum uncertainty in the width of optical beams. Many optical applications such as imaging and beam focusing are limited by the quantum noise in spatial characteristics of light beams.

We present a method to characterize single-photon subtraction process in multiple time-frequency modes. To obtain complete information of the process, we use coherent-state quantum process tomography, and express the results by a quantum process matrix.

A real time, spectrally resolved detection system is developed to characterize the time/frequency modes of an optical frequency comb. Covariance matrix approached is used both for laser dynamics study and quantum metrology experiments.

Multimode squeezed states are used to enhance the measurement of optical frequency fluctuations beyond the standard quantum limit. A multichannel detector is employed, which enables simultaneous extraction of orthogonal parameters characterizing the light field.