scholarly journals Superposed coherent states improve fidelity of NOON states generated in post-selection

2015 ◽  
Vol 93 (4) ◽  
pp. 373-376 ◽  
Author(s):  
S. Sivakumar
Keyword(s):  
Electromagnetic Field ◽  
Coherent State ◽  
Coherent States ◽  
Beam Splitter ◽  
Selection Probability ◽  
Squeezed Vacuum

Mixing the squeezed vacuum and coherent state in a beam splitter generates NOON states of the electromagnetic field, but with fidelity less than unity. In this article it is shown that the output of the beam splitter generates the NOON states with unit fidelity if superposed coherent states are used instead of the squeezed vacuum. Also, the post-selection probability of NOON states is shown to be higher.

scholarly journals Phase estimation with squeezed single photons

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
Stefano Olivares ◽  
Maria Popovic ◽  
Matteo G. A. Paris
Keyword(s):  
Coherent State ◽  
Fisher Information ◽  
Beam Splitter ◽  
Single Photon ◽  
Quantum Fisher Information ◽  
Single Photons ◽  
Squeezed Vacuum ◽  
Vacuum States ◽  
The Difference ◽  
Photocurrent Measurement

AbstractWe address the performance of an interferometric setup in which a squeezed single photon interferes at a beam splitter with a coherent state. Our analysis in based on both the quantum Fisher information and the sensitivity when a Mach-Zehnder setup is considered and the difference photocurrent is detected at the output. We compare our results with those obtained feeding the interferometer with a squeezed vacuum (with the same squeezing parameter of the squeezed single photon) and a coherent state in order to have the same total number of photons circulating in the interferometer. We find that for fixed squeezing parameter and total number of photons there is a threshold of the coherent amplitude interfering with the squeezed single photon above which the squeezed single photons outperform the performance of squeezed vacuum (showing the highest quantum Fisher information). When the difference photocurrent measurement is considered, we can always find a threshold of the squeezing parameter (given the total number of photons and the coherent amplitude) above which squeezed single photons can be exploited to reach a better sensitivity with respect to the use of squeezed vacuum states also in the presence of non unit quantum efficiency.

Coherent States and Classical Limit of Quantum Electrodynamics

2017 ◽  
Author(s):  
Laurent Baulieu ◽  
John Iliopoulos ◽  
Roland Sénéor
Keyword(s):  
Electromagnetic Field ◽  
Quantum Optics ◽  
Coherent State ◽  
Quantum Electrodynamics ◽  
Classical Limit ◽  
Coherent States ◽  
Quantum Fluctuations ◽  
Squeezed States ◽  
Quantum Theories

The coherent state formalism is used in order to study the classical limit of quantum theories and, in particular, quantum electrodynamics. It is shown that we can construct states for which the quantum fluctuations are negligible. Interesting cases include the electromagnetic field in a cavity, or ‘squeezed’ states used in quantum optics.

INTERACTION OF MESOSCOPIC JOSEPHSON JUNCTION WITH A SUCCESSIVE SQUEEZED COHERENT FIELD

2000 ◽  
Vol 14 (16) ◽  
pp. 609-618
Author(s):  
V. A. POPESCU
Keyword(s):  
Coherent State ◽  
Josephson Junction ◽  
Coherent States ◽  
Quantum Noise ◽  
Shapiro Steps ◽  
Superconducting Ring ◽  
Coherent Field ◽  
Current Voltage ◽  
Quantum Current ◽  
The Difference

Signal-to-quantum noise ratio for quantum current in mesoscopic Josephson junction of a circular superconducting ring can be improved if the electromagnetic field is in a successive squeezed coherent state. The mesoscopic Josephson junctions can feel the difference between the successive squeezed coherent states and other types of squeezed coherent states because their current–voltage Shapiro steps are different. We compare our method with another procedure for superposition of two squeezed coherent states (a squeezed even coherent state) and consider the effect of different large inductances on the supercurrent.

scholarly journals Alteration in non-classicality of light on passing through a linear polarization beam splitter

2016 ◽  
Vol 30 (21) ◽  
pp. 1650289
Author(s):  
Namrata Shukla ◽  
Ranjana Prakash
Keyword(s):  
Linear Polarization ◽  
Beam Splitter ◽  
Output Port ◽  
Polarization Beam Splitter ◽  
Stokes Parameters ◽  
Coherent Light ◽  
Squeezed Light ◽  
Squeezed Vacuum

We observe the polarization squeezing in the mixture of a two mode squeezed vacuum and a simple coherent light through a linear polarization beam splitter. Squeezed vacuum not being squeezed in polarization, generates polarization squeezed light when superposed with coherent light. All the three Stokes parameters of the light produced on the output port of polarization beam splitter are found to be squeezed and squeezing factor also depends upon the parameters of coherent light.

scholarly journals Common Coherence Witnesses and Common Coherent States

Entropy ◽  
2021 ◽  
Vol 23 (9) ◽  
pp. 1136
Author(s):  
Bang-Hai Wang ◽  
Zi-Heng Ding ◽  
Zhihao Ma ◽  
Shao-Ming Fei
Keyword(s):  
Coherent State ◽  
Coherent States ◽  
State Problem ◽  
Properties And Characterization ◽  
The Common ◽  
High Level

We show the properties and characterization of coherence witnesses. We show methods for constructing coherence witnesses for an arbitrary coherent state. We investigate the problem of finding common coherence witnesses for certain class of states. We show that finitely many different witnesses W1,W2,⋯,Wn can detect some common coherent states if and only if ∑i=1ntiWi is still a witnesses for any nonnegative numbers ti(i=1,2,⋯,n). We show coherent states play the role of high-level witnesses. Thus, the common state problem is changed into the question of when different high-level witnesses (coherent states) can detect the same coherence witnesses. Moreover, we show a coherent state and its robust state have no common coherence witness and give a general way to construct optimal coherence witnesses for any comparable 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.

Comparative analysis of properties for amplified coherent state and amplified squeezed vacuum

2020 ◽  
Vol 34 (33) ◽  
pp. 2050377
Author(s):  
Yan-Bei Cheng ◽  
Sheng-Guo Guan ◽  
Zu-Jian Wang ◽  
Xue-Xiang Xu
Keyword(s):  
Comparative Analysis ◽  
Coherent State ◽  
Amplification Factor ◽  
Annihilation Operator ◽  
Photon Number ◽  
Matrix Elements ◽  
Squeezed Vacuum ◽  
Quadrature Squeezing ◽  
Antibunching Effect ◽  
Analytical Expressions

Two “amplified” quantum states, that is, amplified coherent state (ACS) and amplified squeezed vacuum (ASV), are considered in this paper by applying operator [Formula: see text] on coherent state (CS) and squeezed vacuum (SV), respectively. Here [Formula: see text] [Formula: see text] denotes a amplification factor and [Formula: see text]) denote the creation (annihilation) operator. Along these two lines, we make a comparative analysis of properties for ACS and ASV. The considered properties include density matrix elements, Wigner function, mean photon number, second-order autocorrelation function, and quadrature squeezing. We derive analytical expressions and make numerical simulations for all the properties. The noteworthy results include: (1) the ACS has antibunching and squeezing characters; (2) the ASV will have the bunching and antibunching effect in small initial squeezing.

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