Quantum-enhanced measurements without entanglement

@article{Braun2018QuantumenhancedMW,
  title={Quantum-enhanced measurements without entanglement},
  author={Daniel Braun and Gerardo Adesso and Fabio Benatti and Roberto Floreanini and Ugo Marzolino and Morgan W. Mitchell and Stefano Pirandola},
  journal={Reviews of Modern Physics},
  year={2018}
}
Quantum-enhanced measurements exploit quantum mechanical effects for increasing the sensitivity of measurements of certain physical parameters and have great potential for both fundamental science and concrete applications. Most of the research has so far focused on using highly entangled states, which are, however, difficult to produce and to stabilize for a large number of constituents. In the following we review alternative mechanisms, notably the use of more general quantum correlations… 

Figures from this paper

Quantum metrology with quantum-chaotic sensors
TLDR
It is shown that large benefits can be drawn from rendering integrable quantum sensors chaotic, both in terms of achievable sensitivity as well as robustness to noise, while avoiding the challenge of preparing and protecting large-scale entanglement.
Effects of Indistinguishability in a System of Three Identical Qubits
Quantum correlations of identical particles are important for quantum-enhanced technologies. The recently introduced non-standard approach to treat identical particles is here exploited to show the
Entanglement of particles versus entanglement of fields: independent quantum resources
TLDR
It is shown that particle entanglement and fieldEntanglement are actually distinct phenomena that can occur and be observed independently and can be characterized together with the exchange symmetry of bosonic and fermionic systems or independently thereof.
Quantum fidelity measures for mixed states.
TLDR
It is shown that there are large classes of measures that satisfy all the required properties of a fidelity measure, just as there are many norms of Hilbert space operators, and many measures of entropy.
Colloquium: quantum coherence as a resource
The coherent superposition of states, in combination with the quantization of observables, represents one of the most fundamental features that mark the departure of quantum mechanics from the
Genuine quantum correlations of quantum many-body systems
Quantum information theory has considerably helped in the understanding of quantum many-body systems. Since the early 2000s various measures of quantum entanglement have been employed to characterise
Thermal quantum metrology in memoryless and correlated environments
In bosonic quantum metrology, the estimate of a loss parameter is typically performed by means of pure states, such as coherent, squeezed or entangled states, while mixed thermal probes are discarded
Indistinguishability-enabled coherence for quantum metrology
Quantum coherence plays a fundamental and operational role in different areas of physics. A resource theory has been developed to characterize the coherence of distinguishable particles systems. Here
Extremal quantum states
The striking differences between quantum and classical systems predicate disruptive quantum technologies. We peruse quantumness from a variety of viewpoints, concentrating on phase-space formulations
Quantum jump metrology
Quantum metrology exploits quantum correlations in specially prepared entangled or other nonclassical states to perform measurements that exceed the standard quantum limit. Typically, though, such
...
...

References

SHOWING 1-10 OF 550 REFERENCES
Quantum Correlations in Mixed-State Metrology
We analyze the effects of quantum correlations, such as entanglement and discord, on the efficiency of phase estimation by studying four quantum circuits that can be readily implemented using NMR
Experimental quantum computing without entanglement.
TLDR
The results show that even fully separable, highly mixed, states can contain intrinsically quantum mechanical correlations and that these could offer a valuable resource for quantum information technologies.
Quantum sensing
“Quantum sensing” describes the use of a quantum system, quantum properties or quantum phenomena to perform a measurement of a physical quantity. Historical examples of quantum sensors include
Measures and applications of quantum correlations
TLDR
This work gives an overview of the current quest for a proper understanding and characterisation of the frontier between classical and quantum correlations (QCs) in composite states, and focuses on various approaches to define and quantify general QCs, based on different yet interlinked physical perspectives.
Entanglement is not a critical resource for quantum metrology
We investigate high-precision measurements beyond the standard quantum limit, utilizing nonclassical states. Although entanglement was considered a resource for achieving the Heisenberg limit in
Non-classical states of atomic ensembles: fundamentals and applications in quantum metrology
Quantum technologies exploit entanglement to revolutionize computing, measurement, and communication. This has stimulated the research in different areas of physics to engineer and manipulate fragile
Quantum entanglement of identical particles by standard information-theoretic notions
TLDR
This work introduces a state-based method which, as second quantization, does not label identical particles and establishes the quantitative role played by arbitrary wave function overlaps, local measurements and particle nature in assessing entanglement by notions commonly used in quantum information theory for distinguishable particles, like partial trace.
Squeezing and entanglement in a Bose–Einstein condensate
TLDR
Spin squeezed states suitable for atomic interferometry are demonstrated by splitting a condensate into a few parts using a lattice potential by implying entanglement between the particles.
Colloquium: quantum coherence as a resource
The coherent superposition of states, in combination with the quantization of observables, represents one of the most fundamental features that mark the departure of quantum mechanics from the
OPEN QUANTUM DYNAMICS: COMPLETE POSITIVITY AND ENTANGLEMENT
We review the standard treatment of open quantum systems in relation to quantum entanglement, analyzing, in particular, the behavior of bipartite systems immersed in the same environment. We first
...
...