Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:cond-mat/0310180 · Science

Detection of Quantum Noise from an Electrically Driven Two-Level System

R. Deblock, Eugen Onac, Leonid Gurevich, Leo P. Kouwenhoven

Published Jul 10, 2003• 176 citations
arXivHTMLPDF

Abstract

The electrical noise of mesoscopic devices can be strongly influenced by the quantum motion of electrons. To probe this effect, we have measured the current fluctuations at high frequency (5 to 90 gigahertz) using a superconductor-insulator-superconductor tunnel junction as an on-chip spectrum analyzer. By coupling this frequency-resolved noise detector to a quantum device, we can measure the high-frequency, nonsymmetrized noise as demonstrated for a Josephson junction. The same scheme is used to detect the current fluctuations arising from coherent charge oscillations in a two-level system, a superconducting charge qubit. A narrow band peak is observed in the spectral noise density at the frequency of the coherent charge oscillations.

DOI
10.1126/science.1084175

Related papers

Detection of quantum noise from mesoscopic devices with an SIS detector

R. Deblock, Eugen Onac, Leonid Gurevich +1 more

Quantum mechanics can strongly influence the noise properties of mesoscopic devices. To probe this effect we have measured the current fluctuations at high-frequency (5-90G Hz) using a superconductor-insulator-superconductor tunnel junction as an on-chip spectrum analyzer. By coupling this frequency-resolved noise detector to a quantum device we can measure the high-frequency, non-symmetrized noise as demonstrated for a Josephson junction. The same scheme has been used to detect the current fluctuations arising from coherent charge oscillations in a two-level system, a superconducting charge qubit. A narrow band peak was observed in the spectral noise density at the frequency of the coherent charge oscillations.

arXiv:cond-mat/0405601•May 26, 2004•0 citations

Emission and Absorption Asymmetry in the Quantum Noise of a Josephson Junction

P.-M. Billangeon, F. Pierre, Hélène Bouchiat +1 more

We measure current fluctuations of mesoscopic devices in the quantum regime, when the frequency is of the order of or higher than the applied voltage or temperature. Detection is designed to probe separately the absorption and emission contributions of current fluctuations, i.e. the positive and negative frequencies of the Fourier transformed nonsymmetrized noise correlator. It relies on measuring the quasiparticles photon assisted tunneling current across a superconductor-insulator-superconductor junction (the detector junction) caused by the excess current fluctuations generated by quasiparticles tunneling across a Josephson junction (the source junction). We demonstrate unambiguously that the negative and positive frequency parts of the nonsymmetrized noise correlator are separately detected and that the excess current fluctuations of a voltage biased Josephson junction present a strong asymmetry between emission and absorption.

arXiv:cond-mat/0508676•Physical Review Letters•Apr 6, 2006•72 citations

High-frequency quantum admittance and noise measurement with an on-chip resonant circuit

J. Basset, Hélène Bouchiat, R. Deblock

By coupling a quantum detector, a superconductor-insulator-superconductor junction, to a Josephson junction via a resonant circuit we probe the high-frequency properties, namely the ac complex admittance and the current fluctuations of the Josephson junction at the resonant frequencies. The admittance components show frequency-dependent singularities related to the superconducting density of states while the noise exhibits a strong frequency dependence, consistent with theoretical predictions. The circuit also allows us to probe separately the emission and absorption noise in the quantum regime of the superconducting resonant circuit at equilibrium. At low temperature the resonant circuit exhibits only absorption noise related to zero-point fluctuations, whereas at higher temperature emission noise is also present.

arXiv:1110.5834•Physical Review B•Feb 27, 2012•32 citations

Emission and Absorption Quantum Noise Measurement with an On-Chip Resonant Circuit

J. Basset, Hélène Bouchiat, R. Deblock

Using a quantum detector, a superconductor-insulator-superconductor junction, we probe separately the emission and absorption noise in the quantum regime of a superconducting resonant circuit at equilibrium. At low temperature the resonant circuit exhibits only absorption noise related to zero point fluctuations, whereas at higher temperature emission noise is also present. By coupling a Josephson junction, biased above the superconducting gap, to the same resonant circuit, we directly measure the noise power of quasiparticles tunneling through the junction at two resonance frequencies. It exhibits a strong frequency dependence, consistent with theoretical predictions.

arXiv:1006.0892•Physical Review Letters•Oct 11, 2010•81 citations

Saturation of two-level systems and charge noise in Josephson junction qubits

Magdalena Constantin, Clare C. Yu, John M. Martinis

We study the charge noise ${S}_{Q}$ in Josephson qubits produced by fluctuating two-level systems (TLSs) with electric-dipole moments in the substrate. The TLSs are driven by an alternating electric field of angular frequency $\ensuremath{\Omega}$ and electric field intensity $I$. It is not widely appreciated that TLS in small qubits can easily be strongly saturated if $I⪢{I}_{c}$, where ${I}_{c}$ is the critical electric field intensity. To investigate the effect of saturation on the charge noise, we express the noise spectral density in terms of density-matrix elements. To determine the dependence of the density-matrix elements on the ratio $I/{I}_{c}$, we find the steady-state solution for the density matrix using the Bloch-Redfield differential equations. We then obtain an expression for the spectral density of charge fluctuations as a function of frequency $f$ and the ratio $I/{I}_{c}$. We find $1/f$ charge noise at low frequencies, and that the charge noise is white (constant) at high frequencies. Using a flat density of states, we find that TLS saturation has no effect on the charge noise at either high or low frequencies.

arXiv:0810.1334•Physical Review B•Mar 20, 2009•35 citations

Qubits as Spectrometers of Quantum Noise

R. J. Schoelkopf, A. A. Clerk, S. M. Girvin +2 more

Electrical engineers and physicists are naturally very interested in noise in circuits, amplifiers and detectors. With the advent of quantum computation and other high frequency electronics operating at low temperatures, we have entered a regime where quantum noise and quantum-limited detectors are important. In this paper we describe the general concept of a two-level system as a quantum spectrum analyzer and apply it to a simple superconducting qubit, the Cooper-pair box. We derive and discuss the quantum noise associated with both a resistor and a classical tunnel junction, and study the effect these noise sources will have on a Cooper-pair box. Finally, we describe a theoretical technique for calculating quantum noise which involves studying the noisy system of interest coupled to a two-level system. We use this technique to calculate and give a heuristic explanation of the quantum charge noise of a normal metal single electron transistor.

arXiv:cond-mat/0210247•Oct 10, 2002•8 citations
The electrical noise of mesoscopic devices can be strongly influenced by the quantum motion of electrons. To probe this effect, we have measured the current fluctuations at high frequency (5 to 90 gigahertz) using a superconductor-insulator-superconductor tunnel junction as an on-chip spectrum analyzer. By coupling this frequency-resolved noise detector to a quantum device, we can measure the high-frequency, nonsymmetrized noise as demonstrated for a Josephson junction. The same scheme is used to detect the current fluctuations arising from coherent charge oscillations in a two-level system, a superconducting charge qubit. A narrow band peak is observed in the spectral noise density at the frequency of the coherent charge oscillations.
Quantum mechanics can strongly influence the noise properties of mesoscopic devices. To probe this effect we have measured the current fluctuations at high-frequency (5-90G Hz) using a superconductor-insulator-superconductor tunnel junction as an on-chip spectrum analyzer. By coupling this frequency-resolved noise detector to a quantum device we can measure the high-frequency, non-symmetrized noise as demonstrated for a Josephson junction. The same scheme has been used to detect the current fluctuations arising from coherent charge oscillations in a two-level system, a superconducting charge qubit. A narrow band peak was observed in the spectral noise density at the frequency of the coherent charge oscillations.
We measure current fluctuations of mesoscopic devices in the quantum regime, when the frequency is of the order of or higher than the applied voltage or temperature. Detection is designed to probe separately the absorption and emission contributions of current fluctuations, i.e. the positive and negative frequencies of the Fourier transformed nonsymmetrized noise correlator. It relies on measuring the quasiparticles photon assisted tunneling current across a superconductor-insulator-superconductor junction (the detector junction) caused by the excess current fluctuations generated by quasiparticles tunneling across a Josephson junction (the source junction). We demonstrate unambiguously that the negative and positive frequency parts of the nonsymmetrized noise correlator are separately detected and that the excess current fluctuations of a voltage biased Josephson junction present a strong asymmetry between emission and absorption.
By coupling a quantum detector, a superconductor-insulator-superconductor junction, to a Josephson junction via a resonant circuit we probe the high-frequency properties, namely the ac complex admittance and the current fluctuations of the Josephson junction at the resonant frequencies. The admittance components show frequency-dependent singularities related to the superconducting density of states while the noise exhibits a strong frequency dependence, consistent with theoretical predictions. The circuit also allows us to probe separately the emission and absorption noise in the quantum regime of the superconducting resonant circuit at equilibrium. At low temperature the resonant circuit exhibits only absorption noise related to zero-point fluctuations, whereas at higher temperature emission noise is also present.
Using a quantum detector, a superconductor-insulator-superconductor junction, we probe separately the emission and absorption noise in the quantum regime of a superconducting resonant circuit at equilibrium. At low temperature the resonant circuit exhibits only absorption noise related to zero point fluctuations, whereas at higher temperature emission noise is also present. By coupling a Josephson junction, biased above the superconducting gap, to the same resonant circuit, we directly measure the noise power of quasiparticles tunneling through the junction at two resonance frequencies. It exhibits a strong frequency dependence, consistent with theoretical predictions.
We study the charge noise SQ{S}_{Q}SQ​ in Josephson qubits produced by fluctuating two-level systems (TLSs) with electric-dipole moments in the substrate. The TLSs are driven by an alternating electric field of angular frequency $\ensuremath{\Omega}$ and electric field intensity III. It is not widely appreciated that TLS in small qubits can easily be strongly saturated if I⪢IcI⪢{I}_{c}I⪢Ic​, where Ic{I}_{c}Ic​ is the critical electric field intensity. To investigate the effect of saturation on the charge noise, we express the noise spectral density in terms of density-matrix elements. To determine the dependence of the density-matrix elements on the ratio I/IcI/{I}_{c}I/Ic​, we find the steady-state solution for the density matrix using the Bloch-Redfield differential equations. We then obtain an expression for the spectral density of charge fluctuations as a function of frequency fff and the ratio I/IcI/{I}_{c}I/Ic​. We find 1/f1/f1/f charge noise at low frequencies, and that the charge noise is white (constant) at high frequencies. Using a flat density of states, we find that TLS saturation has no effect on the charge noise at either high or low frequencies.
Electrical engineers and physicists are naturally very interested in noise in circuits, amplifiers and detectors. With the advent of quantum computation and other high frequency electronics operating at low temperatures, we have entered a regime where quantum noise and quantum-limited detectors are important. In this paper we describe the general concept of a two-level system as a quantum spectrum analyzer and apply it to a simple superconducting qubit, the Cooper-pair box. We derive and discuss the quantum noise associated with both a resistor and a classical tunnel junction, and study the effect these noise sources will have on a Cooper-pair box. Finally, we describe a theoretical technique for calculating quantum noise which involves studying the noisy system of interest coupled to a two-level system. We use this technique to calculate and give a heuristic explanation of the quantum charge noise of a normal metal single electron transistor.