Detection of quantum noise

Gavish, U.; Levinson, Y.; Imry, Y.

doi:10.1103/physrevb.62.r10637

Cited by 140 publications

(168 citation statements)

References 25 publications

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“…So there is, in general, no reason to expect (4.4) to dominate. A heuristic quantum Langevin equation has been used for a system involving a shunted Josephson junction [3,[16][17][18][19][20]. Then Q is the Josephson angle, and with the constant coefficients satisfying I > I 0 .…”

Section: Nonlinear Q Systemsmentioning

confidence: 99%

Conditions for the validity of the quantum Langevin equation

Frenkel

Taylor

2012

Phys. Rev. E

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From microscopic models, a Langevin equation can, in general, be derived only as an approximation. Two possible conditions to validate this approximation are studied. One is, for a linear Langevin equation, that the frequency of the Fourier transform should be close to the natural frequency of the system. The other is by the assumption of "slow" variables. We test this method by comparison with an exactly soluble model and point out its limitations. We base our discussion on two approaches. The first is a direct, elementary treatment of Senitzky. The second is via a generalized Langevin equation as an intermediate step.

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Section: Nonlinear Q Systemsmentioning

confidence: 99%

Conditions for the validity of the quantum Langevin equation

Frenkel

Taylor

2012

Phys. Rev. E

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“…h I t I t i. This definition is valid for both positive and negative frequencies !, corresponding to energy absorption or emission by the device [3][4][5]. When jeVj j@!j; k B T (V is the voltage bias and T the temperature), shot noise dominates over other types of noise and the power density has a white spectrum that can be expressed as S I ÿ!…”

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confidence: 99%

Shot-Noise Detection in a Carbon Nanotube Quantum Dot

et al. 2006

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An on-chip detection scheme for high frequency signals is used to detect noise generated by a quantum dot formed in a single wall carbon nanotube. The noise detection is based on photon assisted tunneling in a superconductor-insulator-superconductor junction. Measurements of shot noise over a full Coulomb diamond are reported with excited states and inelastic cotunneling clearly resolved. Super-Poissonian noise is detected in the case of inelastic cotunneling. DOI: 10.1103/PhysRevLett.96.026803 PACS numbers: 73.63.Kv, 73.23.Hk, 73.63.Fg, 74.40.+k The study of shot noise, i.e., nonequilibrium current fluctuations due to the discreteness of charge carriers, is an important tool for studying correlations induced in mesoscopic transport by different types of interactions [1,2]. Current is characterized by Poissonian shot noise when transport is determined by an uncorrelated stochastic process. Electron-electron interactions, such as Coulomb repulsion or resulting from the Pauli exclusion principle, can correlate electron motion and suppress shot noise. The noise power density is defined as the Fourier transform of the current-current correlator S I ! R 1 ÿ1 d e i! h I t I t i. This definition is valid for both positive and negative frequencies !, corresponding to energy absorption or emission by the device [3][4][5]. When jeVj j@!j; k B T (V is the voltage bias and T the temperature), shot noise dominates over other types of noise and the power density has a white spectrum that can be expressed as S I ÿ! S I ! FeI. Here I is the average current and the Fano factor F indicates the deviation from Poissonian shot noise for which F 1. If the noise detector cannot distinguish between emission and absorption processes, a symmetrized version S symm I ! S I ! S I ÿ! is used. The Schottky formula S symm I 2eI refers to this symmetrized case.For electron transport through a quantum dot (QD), shot noise can be either suppressed or enhanced with respect to the Poissonian value. First, for resonant tunneling, when a QD ground state is aligned between the Fermi levels in the leads, the Fano factor can vary between 1=2 and 1. The exact value is determined by the ratio of tunneling rates between the dot and the two leads [6]. For strongly asymmetric barriers, transport is dominated by the most opaque one and shot noise is Poissonian. If the barriers are symmetric, the resonant charge state is occupied 50% of the time and a F 1=2 shot-noise suppression is predicted. Second, when the QD is in Coulomb blockade, first-order sequential tunneling is energetically forbidden. Transport can still occur via cotunneling processes [7], elastic or inelastic. These are second-order processes, with a virtual intermediate state, allowing electron transfer between the leads. The elastic process leaves the QD in its ground state and transport is Poissonian. Inelastic cotunneling switches the system from a ground to an excited state and can lead to super-Poissonian noise with a Fano factor up to F 3 [8]. Experiments have shown shot-noise suppress...

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“…Equations (2.1.5) and (2.1.6) are fundamental properties of the symmetrised power spectral density so defined, that render it useful (irrespective of whether it is generically measured in an experiment [69,82,83]). …”

Section: Tools To Characterise Fluctuations In Continuous Measurementsmentioning

confidence: 99%

Quantum Limits on Measurement and Control of a Mechanical Oscillator

Sudhir

2018

Springer Theses

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PAR Vivishek SUDHIR JOSEPH CONRAD, Heart of DarknessExperimental physics demands a certain degree of manual dexterity, the patience to tolerate the mundane, and an inexhaustible supply of optimism. Tobias hired me to work on an immensely sophisticated experiment despite any proof of my possessing these qualities; I am indebted to him for the belief he has placed in me. I would also like to acknowledge his dedication to fostering an environment where the pursuit of science is unencumbered by other worldly concerns. Stefan, Ewold and Samuel bore the brunt of a theorist trying to perform delicate experiments; the stern, yet encouraging, stewardship of this trio ensured that I enjoyed the culture shock. Dal Wilson was more than a colleague and a post-doc; his pragmatic approach to physics provided the ideal counter-point in our attempts to forge a deeper understanding of things ranging from vibration isolation to the subtleties of quantum mechanics. Without the patient efforts of Amir, Ryan and Hendrik in designing, fabricating, and testing of devices, none of the results reported here would have been possible. I hope I have been able to bequeath a better vision of the future of our experiment to Sergey. Conversations with Alexey, Daniel and Nathan have enabled me to vicariously learn how to measure microwave "photons". John Jost once taught me how to decorate a Christmas tree; since then he has imparted some wisdom on frequency metrology, and some on atomic physics. Together with Dal, Victor and Caroline have probably spent the most time with me outside the lab; it was fun to exercise an air of social normalcy with this bunch. Christophe has been an amazing sparring partner on every subject capable of being brought under scientific scrutiny.The personal space required for the pursuit of science comes through the sacrifice of many people. My family back home in India -parents, sister, grand-parents -have had to patiently wait for the brief interludes when I go home. No words can do justice to this and the very many other pleasures they have surrendered over the years for my sake. Before physics attracted me, I was charmed by someone else; I am lucky to have married her. Long time friends, mentorsAjith and Subeesh -have played pivotal roles in my being able to engage in physics; I hope to repay this enormous debt, some day.It was a privilege to have learnt from a few great teachers during my formative years. Their vision of an indelible unity in nature continues to motivate my study of physics. vii AbstractThe precision measurement of position has a long-standing tradition in physics. Cavendish's verification of the universal law of gravitation using a torsion pendulum, Perrin's confirmation of the atomic hypothesis via the precise measurement of the Brownian motion, and, the verification of the mechanical effect of electromagnetic radiation, all belong to this classical heritage. Quantum mechanics posits that the measurement of position results in an uncertain momentum; an idea developed to full maturity within the ...

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Detection of quantum noise

Cited by 140 publications

References 25 publications

Conditions for the validity of the quantum Langevin equation

Conditions for the validity of the quantum Langevin equation

Shot-Noise Detection in a Carbon Nanotube Quantum Dot

Quantum Limits on Measurement and Control of a Mechanical Oscillator

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