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:2102.05362 · Physical Review Applied

Fast and Ultrasensitive Electrometer Operating at the Single-Photon Level

Benjamin L. Brock, Juliang Li, S. Kanhirathingal, B. Thyagarajan, M. P. Blencowe, A. J. Rimberg

Published Nov 22, 2021• 5 citations
arXivHTMLPDF

Abstract

Fast, ultrasensitive electrometers have been instrumental to the advancement of basic science. However, many applications (such as readout of quantum-dot-based qubits, and mediation of optomechanical interactions) could benefit from operating such charge sensors at low power. Here the authors demonstrate a charge sensitivity of 14 $\ensuremath{\mu}\phantom{\rule{0}{0ex}}e/\sqrt{\mathrm{Hz}}$ with a cavity-embedded Cooper-pair transistor (CCPT) using 16 aW of power, which corresponds to the single-photon level of the cavity. These results support the feasibility of using a CCPT to mediate an optomechanical interaction that reaches the single-photon strong-coupling regime.

DOI
10.1103/physrevapplied.16.l051004

Related papers

Charge sensitivity of a cavity-embedded Cooper pair transistor in the single-photon quantum noise limit

S. Kanhirathingal, Benjamin L. Brock, A. J. Rimberg +1 more

Using a field operator scattering approach, we analyze the quantum dynamics of an ultrasensitive electrometer - a Cooper pair transistor embedded in a quarter-wave microwave cavity (cCPT). While the cCPT is inherently a strongly nonlinear system, we restrict our present analysis to a necessary first investigation of its linear charge sensing capabilities, limiting to low pump powers corresponding to an average cavity photon number $\lesssim 1$. Assuming realizable cCPT parameters similar to those obtained from a characterization of an actual experimental device (B. L. Brock et al., arXiv:2011.06298), we predict the fundamental, quantum noise-limited charge sensitivity to be $0.12\, \mu{\mathrm{e}}/\sqrt{\mathrm{Hz}}$ when the pumped cavity has an average of one photon and the cCPT is operated close to charge degeneracy. This is to be compared with our first reported charge sensitivity value $14\, \mu{\mathrm{e}}/\sqrt{\mathrm{Hz}}$ in the single-photon regime (B. L. Brock {\it et al}., arXiv:2102.05362)

•Dec 22, 2020•0 citations

Charge sensitivity of a cavity-embedded Cooper pair transistor limited by single-photon shot noise

S. Kanhirathingal, B. L. Brock, A. J. Rimberg +1 more

Using an operator scattering approach, we analyze the quantum dynamics of an ultrasensitive electrometer—a Cooper pair transistor embedded in a quarter-wave microwave cavity (cCPT). While the cCPT is inherently a tunable, strongly nonlinear system affording a diverse range of functionalities, we restrict our present analysis to a necessary first investigation of its linear charge sensing capabilities, limiting to low pump powers corresponding to an average cavity photon number of ≲1. Assuming realizable cCPT parameters [B. L. Brock et al., Phys. Rev. Applied 15, 044009 (2021)], and not including noise from the subsequent amplifier chain, we predict the fundamental, photon shot noise-limited charge sensitivity to be 0.12μe/Hz when the pumped cavity has an average of one photon and the cCPT is operated close to charge degeneracy. This is to be compared with a first reported charge sensitivity value of 14μe/Hz in the single-photon regime [B. L. Brock et al., arXiv:2102.05362 (2021)].

arXiv:2012.12313•Journal of Applied Physics•Sep 17, 2021•3 citations

Fast high-fidelity charge readout by operating a cavity-embedded Cooper-pair transistor in the Kerr bistable regime

B. Thyagarajan, S. Kanhirathingal, Benjamin L. Brock +3 more

Operating the cavity-embedded Cooper-pair transistor (CCPT) in the Kerr bistable regime, we demonstrate single-shot resolution between two charge states that are $0.09e$ apart. The measurement is performed with $94\mathrm{%}$ fidelity in a duration of around $3\phantom{\rule{0.2em}{0ex}}\text{\ensuremath{\mu}}\mathrm{s}$. This is done with a drive power that corresponds to only 20 intracavity photons on average in the high oscillation amplitude state of the CCPT, which is orders of magnitude smaller than that in rf single electron transistors. We find that the limiting factor for this mode of operation of the CCPT is the spontaneous fluctuation-induced switching between the two metastable oscillation amplitude states. We present empirical data on the variation of the switching dynamics with drive parameters and CCPT dc bias.

Physical Review Applied•Jan 31, 2024•3 citations

Fast high-fidelity charge readout by operating the cavity-embedded Cooper pair transistor in the Kerr bistable regime

B. Thyagarajan, S. Kanhirathingal, Brock, Benjamin L. +3 more

Operating the cavity-embedded Cooper pair transistor (cCPT) in the Kerr bistable regime, we demonstrate single-shot resolution between two charge states that are $0.09e$ apart. The measurement is performed with 94$\%$ fidelity in a duration of 3 $μ$s. The drive power at which the measurement is performed corresponds to only 20 intracavity photons on average in the high oscillation amplitude state of the cCPT, which is orders-of-magnitude smaller than that in rf-SETs. We find that the limiting factor for this mode of operation of the cCPT is the spontaneous fluctuation-induced switching between the two metastable oscillation amplitude states. We present empirical data on the variation of the switching dynamics with drive parameters and cCPT DC bias.

arXiv:2301.00110•Dec 31, 2022•0 citations

A cavity-Cooper pair transistor scheme for investigating quantum optomechanics in the ultra-strong coupling regime

A. J. Rimberg, M. P. Blencowe, Andrew D. Armour +1 more

We propose a scheme involving a Cooper pair transistor (CPT) embedded in a superconducting microwave cavity, where the CPT serves as a charge tunable quantum inductor to facilitate ultra-strong coupling between photons in the cavity and a nano- to meso-scale mechanical resonator. The mechanical resonator is capacitively coupled to the CPT, such that mechanical displacements of the resonator cause a shift in the CPT inductance and hence the cavity's resonant frequency. The amplification provided by the CPT is sufficient for the zero point motion of the mechanical resonator alone to cause a significant change in the cavity resonance. Conversely, a single photon in the cavity causes a shift in the mechanical resonator position on the order of its zero point motion. As a result, the cavity-Cooper pair transistor coupled to a mechanical resonator will be able to access a regime in which single photons can affect single phonons and vice versa. Realizing this ultra-strong coupling regime will facilitate the creation of non-classical states of the mechanical resonator, as well as the means to accurately characterize such states by measuring the cavity photon field.

arXiv:1312.7521•New Journal of Physics•May 9, 2014•69 citations

Circuit QED with a quantum-dot charge qubit dressed by Cooper pairs

Laure E. Bruhat, Tino Cubaynes, J. J. Viennot +4 more

Coupling double-quantum-dot circuits to microwave cavities provides a powerful means to control, couple, and manipulate qubits based on the charge or spin of individual electrons. Here, we revisit this standard configuration by adding superconductivity to the circuit. We combine theory and experiment to study a superconductor--double-quantum-dot circuit coupled to microwave cavity photons. First, we use the cavity as a spectroscopic probe. This allows us to determine the low-energy spectrum of the device and to reveal directly Cooper-pair-assisted tunneling between the two dots. Second, we observe a vacuum Rabi splitting which is a signature of strong charge photon coupling and a premiere with carbon-nanotube-based quantum-dot circuits. We show that our circuit design intrinsically combines a set of key features to achieve the strong coupling regime to the cavity. A low charging energy reduces the device sensitivity to charge noise, while sufficient coupling is provided by the shaping of the spectrum of the double quantum dot by the superconducting reservoir. Our findings could be adapted to many other circuit designs and shed light on the coupling of superconducting nanoscale devices to microwave fields.

arXiv:1612.05214•Physical review. B./Physical review. B•Oct 18, 2018•64 citations
Fast, ultrasensitive electrometers have been instrumental to the advancement of basic science. However, many applications (such as readout of quantum-dot-based qubits, and mediation of optomechanical interactions) could benefit from operating such charge sensors at low power. Here the authors demonstrate a charge sensitivity of 14 \ensuremath{\mu}\phantom{\rule{0}{0ex}}e/\sqrt{\mathrm{Hz}} with a cavity-embedded Cooper-pair transistor (CCPT) using 16 aW of power, which corresponds to the single-photon level of the cavity. These results support the feasibility of using a CCPT to mediate an optomechanical interaction that reaches the single-photon strong-coupling regime.
Using a field operator scattering approach, we analyze the quantum dynamics of an ultrasensitive electrometer - a Cooper pair transistor embedded in a quarter-wave microwave cavity (cCPT). While the cCPT is inherently a strongly nonlinear system, we restrict our present analysis to a necessary first investigation of its linear charge sensing capabilities, limiting to low pump powers corresponding to an average cavity photon number ≲1\lesssim 1≲1. Assuming realizable cCPT parameters similar to those obtained from a characterization of an actual experimental device (B. L. Brock et al., arXiv:2011.06298), we predict the fundamental, quantum noise-limited charge sensitivity to be 0.12 μe/Hz0.12\, \mu{\mathrm{e}}/\sqrt{\mathrm{Hz}}0.12μe/Hz​ when the pumped cavity has an average of one photon and the cCPT is operated close to charge degeneracy. This is to be compared with our first reported charge sensitivity value 14 μe/Hz14\, \mu{\mathrm{e}}/\sqrt{\mathrm{Hz}}14μe/Hz​ in the single-photon regime (B. L. Brock {\it et al}., arXiv:2102.05362)
Using an operator scattering approach, we analyze the quantum dynamics of an ultrasensitive electrometer—a Cooper pair transistor embedded in a quarter-wave microwave cavity (cCPT). While the cCPT is inherently a tunable, strongly nonlinear system affording a diverse range of functionalities, we restrict our present analysis to a necessary first investigation of its linear charge sensing capabilities, limiting to low pump powers corresponding to an average cavity photon number of ≲1. Assuming realizable cCPT parameters [B. L. Brock et al., Phys. Rev. Applied 15, 044009 (2021)], and not including noise from the subsequent amplifier chain, we predict the fundamental, photon shot noise-limited charge sensitivity to be 0.12μe/Hz when the pumped cavity has an average of one photon and the cCPT is operated close to charge degeneracy. This is to be compared with a first reported charge sensitivity value of 14μe/Hz in the single-photon regime [B. L. Brock et al., arXiv:2102.05362 (2021)].
Operating the cavity-embedded Cooper-pair transistor (CCPT) in the Kerr bistable regime, we demonstrate single-shot resolution between two charge states that are 0.09e0.09e0.09e apart. The measurement is performed with $94\mathrm{%}$ fidelity in a duration of around $3\phantom{\rule{0.2em}{0ex}}\text{\ensuremath{\mu}}\mathrm{s}$. This is done with a drive power that corresponds to only 20 intracavity photons on average in the high oscillation amplitude state of the CCPT, which is orders of magnitude smaller than that in rf single electron transistors. We find that the limiting factor for this mode of operation of the CCPT is the spontaneous fluctuation-induced switching between the two metastable oscillation amplitude states. We present empirical data on the variation of the switching dynamics with drive parameters and CCPT dc bias.
Operating the cavity-embedded Cooper pair transistor (cCPT) in the Kerr bistable regime, we demonstrate single-shot resolution between two charge states that are 0.09e0.09e0.09e apart. The measurement is performed with 94%\%% fidelity in a duration of 3 μμμs. The drive power at which the measurement is performed corresponds to only 20 intracavity photons on average in the high oscillation amplitude state of the cCPT, which is orders-of-magnitude smaller than that in rf-SETs. We find that the limiting factor for this mode of operation of the cCPT is the spontaneous fluctuation-induced switching between the two metastable oscillation amplitude states. We present empirical data on the variation of the switching dynamics with drive parameters and cCPT DC bias.
We propose a scheme involving a Cooper pair transistor (CPT) embedded in a superconducting microwave cavity, where the CPT serves as a charge tunable quantum inductor to facilitate ultra-strong coupling between photons in the cavity and a nano- to meso-scale mechanical resonator. The mechanical resonator is capacitively coupled to the CPT, such that mechanical displacements of the resonator cause a shift in the CPT inductance and hence the cavity's resonant frequency. The amplification provided by the CPT is sufficient for the zero point motion of the mechanical resonator alone to cause a significant change in the cavity resonance. Conversely, a single photon in the cavity causes a shift in the mechanical resonator position on the order of its zero point motion. As a result, the cavity-Cooper pair transistor coupled to a mechanical resonator will be able to access a regime in which single photons can affect single phonons and vice versa. Realizing this ultra-strong coupling regime will facilitate the creation of non-classical states of the mechanical resonator, as well as the means to accurately characterize such states by measuring the cavity photon field.
Coupling double-quantum-dot circuits to microwave cavities provides a powerful means to control, couple, and manipulate qubits based on the charge or spin of individual electrons. Here, we revisit this standard configuration by adding superconductivity to the circuit. We combine theory and experiment to study a superconductor--double-quantum-dot circuit coupled to microwave cavity photons. First, we use the cavity as a spectroscopic probe. This allows us to determine the low-energy spectrum of the device and to reveal directly Cooper-pair-assisted tunneling between the two dots. Second, we observe a vacuum Rabi splitting which is a signature of strong charge photon coupling and a premiere with carbon-nanotube-based quantum-dot circuits. We show that our circuit design intrinsically combines a set of key features to achieve the strong coupling regime to the cavity. A low charging energy reduces the device sensitivity to charge noise, while sufficient coupling is provided by the shaping of the spectrum of the double quantum dot by the superconducting reservoir. Our findings could be adapted to many other circuit designs and shed light on the coupling of superconducting nanoscale devices to microwave fields.