Publications (28)
Quantum controlled-Z gate for weakly interacting qubits
M. Micuda, R. Starek, I. Straka +5
We propose and experimentally demonstrate a scheme for implementation of a maximally entangling quantum controlled-Z gate between two weakly interacting systems. We conditionally e…
Single-passage read-out of atomic quantum memory
J. Fiurasek, J. Sherson, T. Opatrny +1
A scheme for retrieving quantum information stored in collective atomic spin systems onto optical pulses is presented. Two off-resonant light pulses cross the atomic medium in two…
Experimental test of strongly non-classical character of a noisy squeezed single-photon state
M. Jezek, A. Tipsmark, R. Dong +4
We experimentally verify the quantum non-Gaussian character of a conditionally generated noisy squeezed single-photon state with positive Wigner function. Employing an optimized wi…
Reversibility of continuous-variable quantum cloning
R. Filip, J. Fiurasek, P. Marek
We analyze a reversibility of optimal Gaussian quantum cloning of a coherent state using only local operations on the clones and classical communication between them and p…
Continuously induced coherence without induced emission
J. Rehacek, L. Mista, J. Fiurasek +1
The coherence properties of two downconversion processes continuously coupled via idler beams are analyzed. We find that the amount of which-way information about a signal photon c…
Enhancing the capacity and performance of collective atomic quantum memory
T. Opatrny, J. Fiurasek
Present schemes involving the quantum non-demolition interaction between atomic samples and off-resonant light pulses allow us to store quantum information corresponding to a singl…
Multipartite Asymmetric Quantum Cloning
S. Iblisdir, A. Acin, N. Gisin +3
We investigate the optimal distribution of quantum information over multipartite systems in asymmetric settings. We introduce cloning transformations that take identical replic…
Sampling the canonical phase from phase-space functions
J. Fiurasek, M. Dakna, T. Opatrny +1
We discuss the possibility of sampling exponential moments of the canonical phase from the s-parametrized phase space functions. We show that the sampling kernels exist and are wel…
Heralded noiseless amplification and attenuation of non-gaussian states of light
C. N. Gagatsos, J. Fiurasek, A. Zavatta +2
We examine the behavior of non-Gaussian states of light under the action of probabilistic noiseless amplification and attenuation. Surprisingly, we find that the mean field amplitu…
Light Qubit Storage and Retrieval using Macroscopic Atomic Ensembles
J. Sherson, A. S. Soerensen, J. Fiurasek +2
We present an experimentally feasible protocol for the complete storage and retrieval of arbitrary light states in an atomic quantum memory using the well-established Faraday inter…
Generation of Large Photon-Number Cat States using Linear Optics and Quantum Memory
N. J. Cerf, J. Fiurasek, S. Iblisdir +1
A recursive method for producing path-entangled states of light is presented. These states may find applications in quantum lithography and high-precision interferometric measureme…
Orthogonalization of partly unknown quantum states
M. Jezek, M. Micuda, I. Straka +3
A quantum analog of the fundamental classical NOT gate is a quantum gate that would transform any input qubit state onto an orthogonal state. Intriguingly, this universal NOT gate…
Conditional generation of arbitrary multimode entangled states of light with linear optics
J. Fiurasek, S. Massar, N. J. Cerf
We propose a universal scheme for the probabilistic generation of an arbitrary multimode entangled state of light with finite expansion in Fock basis. The suggested setup involves…
Process fidelity estimation of linear optical quantum CZ gate: A comparative study
M. Micuda, M. Sedlak, I. Straka +4
We present a systematic comparison of different methods of fidelity estimation of a linear optical quantum controlled-Z gate implemented by two-photon interference on a partially p…
Experimental Purification of Single Qubits
M. Ricci, F. De Martini, N. J. Cerf +3
We report the experimental realization of the purification protocol for single qubits sent through a depolarization channel. The qubits are associated with polarization encoded pho…
Finding optimal strategies for minimum-error quantum-state discrimination
M. Jezek, J. Rehacek, J. Fiurasek
We propose a numerical algorithm for finding optimal measurements for quantum-state discrimination. The theory of the semidefinite programming provides a simple check of the optima…
Optimal entanglement-assisted discrimination of quantum measurements
M. Mikova, M. Sedlak, I. Straka +5
We investigate optimal discrimination between two projective single-qubit measurements in a scenario where the measurement can be performed only once. We consider general setting i…
Experimental realization of linear-optical partial SWAP gates
A. Cernoch, J. Soubusta, L. Bartuskova +2
We present a linear-optical implementation of a class of two-qubit partial SWAP gates for polarization states of photons. Different gate operations, including the SWAP and entangli…
Experimental demonstration of continuous variable purification of squeezed states
A. Franzen, B. Hage, J. DiGuglielmo +2
We report on the first experimental demonstration of purification of nonclassical continuous variable states. The protocol uses two copies of phase-diffused states overlapped on a…
Pulsed squeezed vacuum characterization without homodyning
J. Wenger, J. Fiurasek, R. Tualle-Brouri +2
Direct photon detection is experimentally implemented to measure the squeezing and purity of a single-mode squeezed vacuum state without an interferometric homodyne detection. Foll…
Several experimental realizations of symmetric phase-covariant quantum cloner of single-photon qubits
J. Soubusta, L. Bartuskova, A. Cernoch +2
We compare several optical implementations of phase-covariant cloning machines. The experiments are based on copying of the polarization state of a single photon in bulk optics by…
Experimental phase-covariant cloning of polarization states of single photons
A. Cernoch, L. Bartuskova, J. Soubusta +3
The experimental realization of optimal symmetric phase-covariant 1->2 cloning of qubit states is presented. The qubits are represented by polarization states of photons generated…
Slow-light pulses in moving media
J. Fiurasek, U. Leonhardt, R. Parentani
Slow light in moving media reaches a paradoxical regime when the flow speed of the medium approaches the group velocity of light. Pulses can penetrate a region where a counter-prop…
Quantum cloning of orthogonal qubits
J. Fiurasek, S. Iblisdir, S. Massar +1
An optimal universal cloning transformation is derived that produces M copies of an unknown qubit from a pair of orthogonal qubits. For M>6, the corresponding cloning fidelity is h…
Designing optimum CP maps for quantum teleportation
J. Rehacek, Z. Hradil, J. Fiurasek +1
We study general teleportation scheme with an arbitrary state of the pair of particles (2 and 3) shared by Alice and Bob, and arbitrary measurements on the input particle 1 and one…
Loophole-free test of quantum non-locality using high-efficiency homodyne detectors
R. Garcia-Patron, J. Fiurasek, N. J. Cerf
We provide a detailed analysis of the recently proposed setup for a loophole-free test of Bell inequality using conditionally generated non-Gaussian states of light and balanced ho…
Separating the classical and quantum information via quantum cloning
M. Ricci, F. Sciarrino, N. J. Cerf +3
An application of quantum cloning to optimally interface a quantum system with a classical observer is presented, in particular we describe a procedure to perform a minimal disturb…
Proposal for a loophole-free Bell test using homodyne detection
R. Garcia-Patron Sanchez, J. Fiurasek, N. J. Cerf +3
We propose a feasible optical setup allowing for a loophole-free Bell test with efficient homodyne detection. A non-gaussian entangled state is generated from a two-mode squeezed v…