41.10.+p Quantum enhanced measurements

A sensitive electrometer based on a Rydberg atom in a Schrödinger-cat state

Date: 
2016-07-14
Author(s): 

Adrien Facon, Eva-Katharina Dietsche, Dorian Grosso, Serge Haroche, Jean-Michel Raimond, Michel Brune & Sébastien Gleyzes

Reference: 

Nature 535, 262–265 (14 July 2016) doi:10.1038/nature18327

Fundamental quantum fluctuations caused by the Heisenberg principle limit measurement precision.

The Quantum Allan Variance

Date: 
2016-01-07
Author(s): 

Krzysztof Chabuda, Ian Leroux, Rafal Demkowicz-Dobrzanski

In atomic clocks, the frequency of a local oscillator is stabilized based on the feedback signal obtained by periodically interrogating an atomic reference system. The instability of the clock is characterized by the Allan variance, a measure widely used to describe the noise of frequency standards.

Mode engineering for realistic quantum-enhanced interferometry

Date: 
2016-04-29
Author(s): 

Michał Jachura, Radosław Chrapkiewicz, Rafał Demkowicz-Dobrzański, Wojciech Wasilewski, Konrad Banaszek

Reference: 

Nature Communications 7, 11411 (2016) http://arxiv.org/pdf/1504.05435.pdf

Quantum metrology overcomes standard precision limits by exploiting collective quantum superpositions of physical systems used for sensing, with the prominent example of non-classical multiphoton states improving interferometric techniques. Practical quantum-enhanced interferometry is, however, vulnerable to imperfections such as partial distinguishability of interfering photons. Here we introduce a method where appropriate design of the modal structure of input photons can alleviate deleterious effects caused by another, experimentally inaccessible degree of freedom.

The ultimate precision limits for noisy frequency estimation

Date: 
2016-03-24
Author(s): 

Andrea Smirne, Jan Kołodyński, Susana F. Huelga, Rafał Demkowicz-Dobrzański

Reference: 

Phys. Rev. Lett. 116, 120801 (2015) http://arxiv.org/pdf/1511.02708.pdf

Quantum metrology protocols allow us to surpass precision limits typical to classical statistics. However, in recent years, no-go theorems have been formulated, which state that typical forms of uncorrelated noise can constrain the quantum enhancement to a constant factor and, thus, bound the error to the standard asymptotic scaling. In particular, that is the case of time-homogeneous (Lindbladian) dephasing and, more generally, all semigroup dynamics that include phase covariant terms, which commute with the system Hamiltonian.

Quantum interferometric measurements of temperature

Date: 
2015-09-10
Author(s): 

Marcin Jarzyna, Marcin Zwierz

Reference: 

Phys. Rev. A 92, 032112 (2015) http://arxiv.org/abs/1412.5609

We provide a detailed description of the quantum interferometric thermometer, which is a device that estimates the temperature of a sample from the measurements of the optical phase.

Quantum computation speedup limits from quantum metrological precision bounds

Date: 
2015-06-17 - 2016-06-17
Author(s): 

Rafał Demkowicz-Dobrzański, Marcin Markiewicz

Reference: 

Phys. Rev. A 91, 062322 (2015) http://arxiv.org/abs/1412.6111

We propose a scheme for translating metrological precision bounds into lower bounds on query complexity of quantum search algorithms. Within the scheme the link between quadratic performance enhancement in idealized quantum metrological and quantum computing schemes becomes clear.

True precision limits in quantum metrology

Date: 
2015-01-09
Author(s): 

Marcin Jarzyna, Rafał Demkowicz-Dobrzański

Reference: 

New J. Phys. 17, 013010 (2015) http://arxiv.org/abs/1407.4805

We show that quantification of the performance of quantum-enhanced measurement schemes based on the concept of quantum Fisher information (QFI) yields results that are asymptotically equivalent to those from the rigorous Bayesian approach, provided generic uncorrelated noise is present in the setup.

Usefulness of an enhanced Kitaev phase-estimation algorithm in quantum metrology and computation

Date: 
2014-11-17
Author(s): 

Tomasz Kaftal, Rafał Demkowicz-Dobrzański

Reference: 

Phys. Rev. A 90, 062313 (2014) http://arxiv.org/abs/1405.5897

We analyze the performance of a generalized Kitaev’s phase-estimation algorithm where N phase gates, acting on M qubits prepared in a product state, may be distributed in an arbitrary way. Unlike the standard algorithm, where the mean square error scales as 1/N, the optimal generalizations offer the Heisenberg 1/N2 error scaling and we show that they are in fact very close to the fundamental Bayesian estimation bound.

Using Entanglement Against Noise in Quantum Metrology

Date: 
2014-12-19
Author(s): 

Rafal Demkowicz-Dobrzański, Lorenzo Maccone

Reference: 

Phys. Rev. Lett. 113, 250801 (2014) http://arxiv.org/abs/1407.2934

We analyze the role of entanglement among probes and with external ancillas in quantum metrology. In the absence of noise, it is known that unentangled sequential strategies can achieve the same Heisenberg scaling of entangled strategies and that external ancillas are useless.

Bayesian quantum frequency estimation in presence of collective dephasing

Date: 
2014-06-18 - 2014-10-31
Author(s): 

Katarzyna Macieszczak, Martin Fraas, Rafał Demkowicz-Dobrzański

Reference: 

New J. Phys. 16, 113002 (2014)

We advocate a Bayesian approach to optimal quantum frequency estimation—an important issue for future quantum enhanced atomic clock operation. The approach provides a clear insight into the interplay between decoherence and the extent of prior knowledge in determining the optimal interrogation times and optimal estimation strategies.

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