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92

Jul 20, 2013
07/13

by
Miroslav Jezek; Ivo Straka; Michal Micuda; Miloslav Dusek; Jaromir Fiurasek; Radim Filip

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We report on experimental verification of quantum non-Gaussianity of a heralded single photon state with positive Wigner function. We unambiguously demonstrate that the generated state cannot be expressed as a mixture of Gaussian states. A sufficient information to witness the quantum non-Gaussianity is obtained from a standard photon anti-correlation measurement.

Source: http://arxiv.org/abs/1107.4305v1

11
11

Jun 28, 2018
06/18

by
Ivo Straka; Martina Miková; Michal Mičuda; Miloslav Dušek; Miroslav Ježek; Radim Filip

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We propose and experimentally verify a cooling limit for a quantum channel going through an incoherent environment. The environment consists of a large number of independent non-interacting and non-interfering elementary quantum systems - qubits. The qubits travelling through the channel can only be randomly replaced by environmental qubits. We investigate a conditional cooling limit that exploits an additional probing output. The limit specifies when the single-qubit channel is quantum, i.e....

Topic: Quantum Physics

Source: http://arxiv.org/abs/1509.03144

51
51

Sep 23, 2013
09/13

by
Martina Mikova; Helena Fikerova; Ivo Straka; Michal Micuda; Miroslav Jezek; Miloslav Dusek

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We have successfully used a fast electronic feed forward to increase the success probability of a linear optical implementation of a programmable phase gate from 25% to its theoretical limit of 50%. The feed forward applies a conditional unitary operation which changes the incorrect output states of the data qubit to the correct ones. The gate itself rotates an arbitrary quantum state of the data qubit around the z-axis of the Bloch sphere with the angle of rotation being fully determined by...

Source: http://arxiv.org/abs/1111.3237v1

5
5.0

Jun 30, 2018
06/18

by
Michal Micuda; Ester Dolakova; Ivo Straka; Martina Mikova; Miloslav Dusek; Jaromir Fiurasek; Miroslav Jezek

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We experimentally demonstrate optical Mach-Zehnder interferometer utilizing displaced Sagnac configuration to enhance its phase stability. The interferometer with footprint of 27x40 cm offers individually accessible paths and shows phase deviation less than 0.4 deg during a 250 s long measurement. The phase drift, evaluated by means of Allan deviation, stays below 3 deg or 7 nm for 1.5 hours without any active stabilization. The polarization insensitive design is verified by measuring...

Topics: Physics, Quantum Physics, Optics

Source: http://arxiv.org/abs/1407.5207

4
4.0

Jun 29, 2018
06/18

by
Ivo Straka; Lukáš Lachman; Josef Hloušek; Martina Miková; Michal Mičuda; Miroslav Ježek; Radim Filip

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Quantum nature of light has complex properties that are required for many key efforts in quantum optical technology. Sixty years ago, the basic properties of ideal coherent light have been recognized as only classical, while quantum theory allowed reaching more engaging states of light. Nowadays, generating nonclassical light has become a routine for optical laboratories, but quantum states with precise number of photons (Fock states) still pose a challenge. We introduce an experimental...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1611.02504

53
53

Sep 18, 2013
09/13

by
Martina Mikova; Helena Fikerova; Ivo Straka; Michal Micuda; Miroslav Jezek; Miloslav Dusek; Radim Filip

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We have studied how the quality of transfer of a qubit state depends on distinguishability of internal states of the particles carrying qubits. The transfer is implemented without any direct interaction, just by a partial exchange of photons, measurement on one of them, and conditional feed-forward correction. It appears that the quality of the transfer is only influenced by the level of distinguishability of the states of unaccessible internal degrees of freedom not used for information...

Source: http://arxiv.org/abs/1209.0908v2

6
6.0

Jun 29, 2018
06/18

by
Martina Miková; Ivo Straka; Michal Mičuda; Vojtěch Krčmarský; Miloslav Dušek; Miroslav Ježek; Jaromír Fiurášek; Radim Filip

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One of the strengths of quantum information theory is that it can treat quantum states without referring to their particular physical representation. In principle, quantum states can be therefore fully swapped between various quantum systems by their mutual interaction and this quantum state transfer is crucial for many quantum communication and information processing tasks. In practice, however, the achievable interaction time and strength are often limited by decoherence. Here we propose and...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1606.09409

3
3.0

Jun 29, 2018
06/18

by
Michal Mičuda; Robert Stárek; Petr Marek; Martina Miková; Ivo Straka; Miroslav Ježek; Toshiyuki Tashima; Şahin K. Özdemir; Mark Tame

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We experimentally characterize a quantum photonic gate that is capable of converting multiqubit entangled states while acting only on two qubits. It is an important tool in large quantum networks, where it can be used for re-wiring of multipartite entangled states or for generating various entangled states required for specific tasks. The gate can be also used to generate quantum information processing resources, such as entanglement and discord. In our experimental demonstration, we converted...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1610.04504

3
3.0

Jun 30, 2018
06/18

by
Ivo Straka; Ana Predojević; Tobias Huber; Lukáš Lachman; Lorenz Butschek; Martina Miková; Michal Mičuda; Glenn S. Solomon; Gregor Weihs; Miroslav Ježek; Radim Filip

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We introduce and experimentally explore the concept of quantum non-Gaussian depth of single-photon states with a positive Wigner function. The depth measures the robustness of a single-photon state against optical losses. The directly witnessed quantum non-Gaussianity withstands significant attenuation, exhibiting a depth of 18 dB, while the nonclassicality remains unchanged. Quantum non-Gaussian depth is an experimentally approachable quantity that is much more robust than the negativity of...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1403.4194