scholarly journals Phase estimation of coherent states with a noiseless linear amplifier

2017 ◽  
Vol 15 (01) ◽  
pp. 1750009 ◽  
Author(s):  
Syed M. Assad ◽  
Mark Bradshaw ◽  
Ping Koy Lam
Keyword(s):  
Coherent States ◽  
Quantum Fisher Information ◽  
Quantum States ◽  
Phase Estimation ◽  
Linear Amplification ◽  
Output State ◽  
Linear Amplifier ◽  
Phase Estimate ◽  
The Cost ◽  
Probabilistic Protocols

Amplification of quantum states is inevitably accompanied with the introduction of noise at the output. For protocols that are probabilistic with heralded success, noiseless linear amplification in theory may still be possible. When the protocol is successful, it can lead to an output that is a noiselessly amplified copy of the input. When the protocol is unsuccessful, the output state is degraded and is usually discarded. Probabilistic protocols may improve the performance of some quantum information protocols, but not for metrology if the whole statistics is taken into consideration. We calculate the precision limits on estimating the phase of coherent states using a noiseless linear amplifier by computing its quantum Fisher information and we show that on average, the noiseless linear amplifier does not improve the phase estimate. We also discuss the case where abstention from measurement can reduce the cost for estimation.

Teleportation improvement by noiseless linear amplification

2019 ◽  
Vol 19 (11&12) ◽  
pp. 935-951
Author(s):  
Hamza Adnane ◽  
Matteo G.A. Paris
Keyword(s):  
Coherent States ◽  
Large Range ◽  
Low Energy ◽  
Entangled State ◽  
Continuous Variables ◽  
Linear Amplification ◽  
Gaussian States ◽  
Linear Amplifier ◽  
Twin Beam ◽  
Non Gaussian

We address de-Gaussification of continuous variables Gaussian states by optimal non-deterministic noiseless linear amplifier (NLA) and analyze in details the properties of the amplified states. In particular, we investigate the entanglement content and the non-Gaussian character for the class of non-Gaussian entangled state obtained by using NL-amplification of two-mode squeezed vacua (twin-beam, TWB). We show that entanglement always increases, whereas improved EPR correlations are observed only when the input TWB has low energy. We then examine a Braunstein-Kimble-like protocol for the teleportation of coherent states, and compare the performances of TWB-based teleprotation with those obtained using NL-amplified resources. We show that teleportation fidelity and security may be improved for a large range of NLA parameters (gain and threshold).

scholarly journals Non-Gaussianity of quantum states: An experimental test on single-photon-added coherent states

2010 ◽  
Vol 82 (6) ◽  
Author(s):  
Marco Barbieri ◽  
Nicolò Spagnolo ◽  
Marco G. Genoni ◽  
Franck Ferreyrol ◽  
Rémi Blandino ◽  
...  
Keyword(s):  
Experimental Test ◽  
Coherent States ◽  
Single Photon ◽  
Quantum States

Homodyne-like detection scheme based on photon-number-resolving detectors

2017 ◽  
Vol 15 (08) ◽  
pp. 1740016 ◽  
Author(s):  
Alessia Allevi ◽  
Matteo Bina ◽  
Stefano Olivares ◽  
Maria Bondani
Keyword(s):  
Coherent States ◽  
Beam Splitter ◽  
Photon Number ◽  
Local Oscillator ◽  
Quantum States ◽  
Homodyne Detection ◽  
Detection Scheme ◽  
Light Signals ◽  
The Difference ◽  
Signal Field

Homodyne detection is the most effective detection scheme employed in quantum optics to characterize quantum states. It is based on mixing at a beam splitter the signal to be measured with a coherent state, called the “local oscillator,” and on evaluating the difference of the photocurrents of two photodiodes measuring the outputs of the beam splitter. If the local oscillator is much more intense than the field to be measured, the homodyne signal is proportional to the signal-field quadratures. If the local oscillator is less intense, the photodiodes can be replaced with photon-number-resolving detectors, which have a smaller dynamics but can measure the light statistics. The resulting new homodyne-like detector acquires a hybrid nature, being it capable of yielding information on both the particle-like (statistics) and wave-like (phase) properties of light signals. The scheme has been tested in the measurement of the quadratures of coherent states, bracket states and phase-averaged coherent states at different intensities of the local oscillator.

PARASUPERSYMMETRIC COHERENT STATES FOR LANDAU LEVELS WITH DYNAMICAL SYMMETRY GROUP H4

2002 ◽  
Vol 17 (28) ◽  
pp. 4081-4093 ◽  
Author(s):  
H. FAKHRI ◽  
H. MOTAVALI
Keyword(s):  
Magnetic Field ◽  
Symmetry Group ◽  
Coherent States ◽  
Ad Hoc ◽  
Flat Surface ◽  
Arbitrary Order ◽  
Dynamical Symmetry ◽  
Quantum States ◽  
Landau Levels ◽  
Lowering Operator

The eigenstates and their degeneracy for parasupersymmetric Hamiltonian of arbitrary order p, corresponding to the motion of a charged particle with spin [Formula: see text] on the flat surface in the presence of a constant magnetic field along z-axis, are calculated. The eigenstates are expressed in terms of Landau levels quantum states with dynamical symmetry group H4. Furthermore, parasupersymmetric coherent states with multiplicity degeneracy are derived for an ad hoc lowering operator of the eigenstates in terms of ordinary coherent states of Landau Hamiltonian.

scholarly journals Robust Phase Estimation of Gaussian States in the Presence of Outlier Quantum States

2020 ◽  
Vol 10 (16) ◽  
pp. 5475
Author(s):  
Yukito Mototake ◽  
Jun Suzuki
Keyword(s):  
Coherent State ◽  
Quantum System ◽  
Robust Statistics ◽  
Quantum States ◽  
Phase Estimation ◽  
Gaussian States ◽  
Statistical Framework

In this paper, we investigate the problem of estimating the phase of a coherent state in the presence of unavoidable noisy quantum states. These unwarranted quantum states are represented by outlier quantum states in this study. We first present a statistical framework of robust statistics in a quantum system to handle outlier quantum states. We then apply the method of M-estimators to suppress untrusted measurement outcomes due to outlier quantum states. Our proposal has the advantage over the classical methods in being systematic, easy to implement, and robust against occurrence of noisy states.

COLLAPSE AND REVIVAL EFFECT IN A MESOSCOPIC LC CIRCUIT

2004 ◽  
Vol 18 (08) ◽  
pp. 1217-1224 ◽  
Author(s):  
HAI-MEI LUO ◽  
YING-HUA JI ◽  
JIE LIU
Keyword(s):  
Time Evolution ◽  
Dynamic Behavior ◽  
Quantum State ◽  
Tunnel Junction ◽  
Coherent States ◽  
The State ◽  
Quantum States ◽  
Quantum Superposition ◽  
Coupling Energy ◽  
Lc Circuit

This paper studied the time evolution of quantum state in a mesoscopic LC circuit with the coupling energy caused by mesoscopic capacitor acting as a tunnel junction. It indicates that the state of the junction evolves into the quantum superposition of two coherent states and, in the state, nonclassical squeezing properties of the circuit appear. It also indicates that the dynamic behavior of the current shows collapse and revival phenomenon. The research in the paper will be helpful to miniaturize integrate circuits and electric components. It will be also important for the utilization of mesoscopic circuits to evolve the quantum states, which work as information carriers.

scholarly journals A CLASS OF QUANTUM STATES WITH CLASSICAL-LIKE EVOLUTION

1994 ◽  
Vol 08 (29) ◽  
pp. 1823-1831 ◽  
Author(s):  
SALVATORE DE MARTINO ◽  
SILVIO DE SIENA ◽  
FABRIZIO ILLUMINATI
Keyword(s):  
Quantum Mechanics ◽  
Harmonic Oscillator ◽  
Coherent States ◽  
Quantum States ◽  
Time Dependent ◽  
Stationary States ◽  
Oscillator Potential ◽  
Classical Motion ◽  
Stochastic Formulation ◽  
New States

In the framework of the stochastic formulation of quantum mechanics we derive non-stationary states for a class of time-dependent potentials. The wave packets follow a classical motion with constant dispersion. The new states define a possible extension of the harmonic oscillator coherent states. As an explicit application, we study a sestic oscillator potential.

Linear Amplifier and the Coherent States Superpositions

2001 ◽  
Vol 63 (5) ◽  
pp. 372-378 ◽  
Author(s):  
Gamal M Abd Al-Kader
Keyword(s):  
Coherent States ◽  
Linear Amplifier
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