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Quantum metrology from a quantum information science perspective

Géza Tóth, Iagoba Apellaniz
2014 Journal of Physics A: Mathematical and Theoretical  
We discuss some applications of the quantum Fisher information, such as how it can be used to obtain a criterion for a quantum state to be a macroscopic superposition.  ...  Then, we present the fundamental notions of quantum metrology, such as shot-noise scaling, Heisenberg scaling, the quantum Fisher information and the Cramer-Rao bound.  ...  superposition Speed of the quantum evolution 5 The effect of noise 6 Conclusions 28 / 41 Quantum Fisher information and entanglement Bound for separable states A.  ... 
doi:10.1088/1751-8113/47/42/424006 fatcat:5pgkp23fa5bsvixltuoq4gsk5q

On the Use of Classical and Quantum Fisher Information in Molecular Magnetism

Filippo Troiani
2016 Magnetochemistry  
The quantum Fisher information also quantifies the degree of macroscopicity of a quantum state.  ...  As illustrative examples of such applications, we compute the classical and quantum Fisher information of the Fe 4 molecular nanomagnet, used as a probe of an applied magnetic field or as a platform for  ...  Results Fisher Information The Fisher information F is defined for a given dependence on the parameter λ of the quantum state |ψ λ (or ρ λ , in the case of a mixed state), and for a given observable  ... 
doi:10.3390/magnetochemistry2030033 fatcat:p63jue5mizaqdei3k74apl5xby

Quantum Fisher Information of Several Qubitsin the Superposition of A GHZ and two W Stateswith Arbitrary Relative Phase

Fatih Ozaydin, Azmi Ali Altintas, Sinan Bugu, Can Yesilyurt, Metin Arik
2014 International Journal of Theoretical Physics  
We study the quantum Fisher information (QFI) of a system of several particles which is in a superposition of a GHZ and two W states with arbitrary relative phase.  ...  We also analyze the QFI for the state for several instances of N due to the change of the relative phases.  ...  In conclusion, we have studied the quantum Fisher information of a state of several qubits in the superposition of GHZ and W states with relative phases.  ... 
doi:10.1007/s10773-014-2119-4 fatcat:du7djxulf5gqnap5np4o6q4pae

Size of linear superpositions in molecular nanomagnets

F. Troiani, P. Zanardi
2013 Physical Review B  
Exploiting quantum-information theoretic measures, we quantify here the size of linear superpositions that can be generated within the ground multiplet of high- and low-spin nanomagnets.  ...  The actual character (micro or macroscopic) of linear superpositions in low-spin systems is inherently ill-defined.  ...  Acknowledgements This work has been financially support by the FIRB project RBFR12RPD1 of the Italian MIUR, by the ARO MURI grant W911NF-11-1-0268, and by NSF grant numbers PHY-969969 and PHY-803304.  ... 
doi:10.1103/physrevb.88.094413 fatcat:te5tmsf2pjdrjfg4t3mdn2f53i

Effect of phase noise on quantum correlations in Bose-Josephson junctions

G. Ferrini, D. Spehner, A. Minguzzi, F. W. J. Hekking
2011 Physical Review A. Atomic, Molecular, and Optical Physics  
To this aim we compute the squeezing parameter and the quantum Fisher information during the quenched dynamics.  ...  For instance, squeezed states are formed at short times and macroscopic superpositions of phase states at later times.  ...  Smerzi for useful discussions, and P. Hyllus for suggesting us Ref. [43] . We acknowledge financial support from CNRS, the MIDAS project, the Handy-Q project, and the project ANR-09-BLAN-0098-01.  ... 
doi:10.1103/physreva.84.043628 fatcat:zqku2a6dujer7k5tmf67b7l6le

Measures of macroscopicity for quantum spin systems

Florian Fröwis, Wolfgang Dür
2012 New Journal of Physics  
First, we motivate the Fisher information as a measure for the macroscopicity of quantum states. Second, we compare the existing literature of this topic.  ...  We investigate the notion of "macroscopicity" in the case of large quantum spin systems and provide two main results.  ...  Acknowledgments The authors thank Oriol Romero-Isart, Anika Pflanzer and Johannes Kofler for useful discussions and Tomoyuki Morimae for comments on the manuscript and advising us of references [26]  ... 
doi:10.1088/1367-2630/14/9/093039 fatcat:v5iaeq2dhfajbdcoudm5o7qqtm

Disturbance-based measure of macroscopic coherence

Hyukjoon Kwon, Chae-Yeun Park, Kok Chuan Tan, Hyunseok Jeong
2017 New Journal of Physics  
We show that our measure can also quantify the fragility of a quantum state to a certain type of decoherence.  ...  Based on our measure, we point out that recently proposed criteria of macroscopic coherence may lead to inconsistent results when considering certain states such as a product of microscopic superpositions  ...  We evaluate both the bounds for a decohered GHZ-state in a spin system given by In this case, the quantum Fisher information and Wigner-Yanase-Dyson skew information are given by r = G a a I A ,  ... 
doi:10.1088/1367-2630/aa68f5 fatcat:gubdafh2pbaubflwzqnfuyxrpy

Quantum Fisher Information of Decohered W and GHZ Superposition States with Arbitrary Relative Phase

Volkan Erol
2017 International Journal of Theoretical Physics  
In this work, we study the changes in quantum Fisher information (QFI) values for one relative arbitrary phased quantum system consisting of a superposition of N Qubits W and GHZ states.  ...  Quantum Fisher Information (QFI) is a very useful concept for analyzing situations that require phase sensitivity. It become a popular topic especially in Quantum Metrology domain.  ...  Conclusion We studied the changes in QFI values for a useful quantum system state which is a superposition of WN and GHZN states where N=3, 4 and 5.  ... 
doi:10.1007/s10773-017-3487-3 fatcat:afjzofxpmrflxd5fpozyiesbwi

Progress towards macroscopic spin and mechanical superposition via Rydberg interaction

Mohammadsadegh Khazali
2018 Physical Review A  
This paper is a proposal for the generation of many-body entangled state in atomic and mechanical systems.  ...  Dipole coupling between Rydberg atoms and charged cantilevers is proposed for the transfer of the generated superposition to far separated mechanical oscillators.  ...  Measure of Macroscopicity The macroscopicity of quantum state could be quantified using quantum Fisher information.  ... 
doi:10.1103/physreva.98.043836 fatcat:d2oefzv47bbz5g6bknnrots7kq

Measurement- and comparison-based sizes of Schrödinger cat states of light

T. J. Volkoff, K. B. Whaley
2014 Physical Review A. Atomic, Molecular, and Optical Physics  
We also apply earlier comparison-based methods for determining macroscopic superposition size that require a reference GHZ state.  ...  These effective cat-size measures depend on determining the maximal quantum distinguishability of certain states associated with the superposition state: e.g., in one measure, the maximal distinguishability  ...  ACKNOWLEDGMENTS We thank the Kavli Institute for Theoretical Physics program "Control of Complex Quantum Systems" for hospitality and for supporting this research in part by the National Science Foundation  ... 
doi:10.1103/physreva.89.012122 fatcat:whnyveykajdd5imoaru7asmltm

Macroscopic quantum states: Measures, fragility, and implementations

Florian Fröwis, Pavel Sekatski, Wolfgang Dür, Nicolas Gisin, Nicolas Sangouard
2018 Reviews of Modern Physics  
The role of macroscopic quantum states in foundational questions as well as practical applications is outlined.  ...  With recent experimental progress and the aspiration for quantum enhanced applications, the interest in macroscopic quantum effects has been reinforced.  ...  PP00P2_150579, the Quantum Science and Technology (QSIT), and the Austrian Science Fund (FWF) through Project No. P28000-N27.  ... 
doi:10.1103/revmodphys.90.025004 fatcat:5ebcaz2itreyfauzo6puk3gqkq

Are Cloned Quantum States Macroscopic?

F. Fröwis, W. Dür
2012 Physical Review Letters  
We investigate the applicability of cloned states for parameter estimation in the presence of different kinds of noise.  ...  This is indicated by calculating several measures for macroscopic superpositions from the literature, as well as by investigating the distinguishability of the two superposed cloned states.  ...  The quantum Fisher information F of the pure cloned state |ψ from Eq. (2) scales with N 2 [21] , which is optimal for local H (see e.g.  ... 
doi:10.1103/physrevlett.109.170401 pmid:23215165 fatcat:hbrdrhqgvzb3zirfqj7sauvrlm

Quantum thermometry with trapped ions

Peter A. Ivanov
2019 Optics Communications  
Moreover, we show that the non-classical part of the quantum Fisher information could leads to enhancement of the temperature sensitivity compared to the single ion case.  ...  We show that thanks to the laser induced laser coupling between the vibrational modes and the collective spin states the estimation of the temperature is carried out by set of measurements of the spin  ...  In present context the quantum Fisher information is a measure of distinguishability of two quantum states with respect to the infinitesimal variation of the temperature [28] .  ... 
doi:10.1016/j.optcom.2018.12.013 fatcat:wl6arl5qpzgrdeoffkhrua7gjy

Suppressing nonadiabatic transitions during adiabatic generation of highly entangled states in bosonic Josephson junctions

Takuya Hatomura
2019 Physical Review A  
We study suppression of nonadiabatic transitions during adiabatic generation of a cat-like state (a superposition of different size cat states) and a spin squeezed state in a bosonic Josephson junction  ...  For creation of a cat-like state, divergence of the quantum geometric tensor associated with gap closing at the critical point is avoided because of the parity conservation.  ...  According to these schedules, we observe increase of quantum Fisher information for a generated cat state and decrease of the spin squeezing parameter for a generated spin squeezed state, which represent  ... 
doi:10.1103/physreva.100.043619 fatcat:5xeroifljvfz5fe3ilmtrvlowm

Optical implementation of spin squeezing

Takafumi Ono, Javier Sabines-Chesterking, Hugo Cable, Jeremy L O'Brien, Jonathan C F Matthews
2017 New Journal of Physics  
The Fisher information for all photon-number outcomes shows it is possible to obtain a quantum advantage of 1.58 compared to the shot-noise limit, even though due to experimental imperfection, the average  ...  Our demonstration implies improved performance of spin squeezing for applications to quantum metrology.  ...  W911NF-14-1-0133, US Air Force Office of Scientific Research (AFOSR) and the Centre for Nanoscience and Quantum Information (NSQI).  ... 
doi:10.1088/1367-2630/aa6e39 fatcat:au7lbx3dyffedev3pv3nhwpmuq
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