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:2606.03639

Demonstration of a Spherical Penning Trap for Single Electrons

Zirui Fang, Xing Fan

physics.atom-phhep-exquant-phSubmitted Jun 2, 2026• Announced Jun 3, 2026
v1 · Jun 2, 2026v2 · Jun 8, 2026
arXivHTMLPDF

Abstract

A spherical Penning trap has well-separated, clean microwave resonances, making it attractive for precision measurements of the electron magnetic moment and for dark-photon and axion searches with trapped electrons. We demonstrate single-electron trapping in a spherical Penning trap and characterize its microwave resonance structure. The design, single-electron detection, microwave mode characterization, and advantages of this geometry are presented.

Comments
7 pages, 4 figures

Related papers

Single Microwave Photon Detection with a Trapped Electron

April Cridland Mathad, John H. Lacy, Jonathan Pinder +1 more

We investigate theoretically the use of an electron in a Penning trap as a detector of single microwave photons. At the University of Sussex we are developing a chip Penning trap technology, designed to be integrated within quantum circuits. Microwave photons are guided into the trap and interact with the electron’s quantum cyclotron motion. This is an electric dipole transition, where the near field of the microwave radiation induces quantum jumps of the cyclotron harmonic oscillator. The quantum jumps can be monitored using the continuous Stern-Gerlach effect, providing the quantum non demolition signal of the microwave quanta. We calculate the quantum efficiency of photon detection and discuss the main features and technical challenges for the trapped electron as a quantum microwave sensor.

Photonics•Nov 19, 2016•18 citations

Eliminating cavity shifts from electron magnetic moment (g-2) measurements

G. Gabrielse

A cylindrical Penning trap is of such high quality that a single electron is observed with good signal-to-noise. The trap is also a good approximation to an ideal cylindrical microwave cavity. This is documented in situ at 4 K with a new probe utilizing trapped electrons. An extraordinary control of the cavity-electron interaction results and opens the way to a new generation of electron magnetic moment measurements, not limited by either cavity frequency shifts or damping widths, and to sideband cooling of an electron motion to very low (mK) temperatures.

Bulletin of the American Physical Society•May 1, 1993•0 citations

Single Electrons in a Dual-Plane Printed-Circuit-Board Penning Trap

Zirui Fang, Benedict A. D. Sukra, Xing Fan

We demonstrate single-electron trapping and detection in a two-dimensionally scalable dual-plane printed-circuit-board Penning trap. We characterize deterministic electron loading, axial damping, axial temperature, and collision-induced magnetron-radius growth at low magnetic fields. These results establish a practical platform for planar Penning traps and identify key next steps toward applications in quantum information science.

quant-pharXiv:2606.28078•Jun 29, 2026•0 citations

Quantum-logic spectroscopy of an electron or positron for precise tests of the standard model

Xing Fan, Atsushi Noguchi, Kento Taniguchi

We propose a scheme for quantum-logic spectroscopy of an electron or positron in a Penning trap. An electron or positron in a spectroscopy trap is coupled to a remote logic electron or positron via a wire to achieve motional entanglement. By separating the two traps, one can significantly improve magnetic field homogeneity, microwave characteristics, and detection sensitivity. The proposed scheme will improve the measurement precision of the electron's and positron's magnetic moments and charge-to-mass ratios, enabling precise tests of the standard model of particle physics.

arXiv:2502.14157•Physical Review A•Apr 7, 2025•3 citations

Cavity control in a single-electron quantum cyclotron

David Hanneke

A single electron in a quantum cyclotron yields new measurements of the electron magnetic moment, given by g/2 = 1.00115965218073(28)[0.28 ppt], and the fine structure constant, α −1 = 137.035999084(51)[0.37 ppb], both significantly improved from prior results. The static magnetic and electric fields of a Penning trap confine the electron, and a 100 mK dilution refrigerator cools its cyclotron motion to the quantum-mechanical ground state. A quantum nondemolition measurement allows resolution of single cyclotron jumps and spin flips by coupling the cyclotron and spin energies to the frequency of the axial motion, which is self-excited and detected with a cryogenic amplifier. The trap electrodes form a high-Q microwave resonator near the cyclotron frequency; coupling between the cyclotron motion and cavity modes can inhibit spontaneous emission by over 100 timesthe free-space rate and shiftthe cyclotron frequency, a systematic effect that dominated the uncertainties of previous g-value measurements. A cylindrical trap geometry creates cavity modes with analytically calculable couplingsto cyclotron motion. Two independent methods use the cyclotron damping rate of an electron plasma or of the single electron itself as probes of the cavity mode structure and allow the identification ofthe modes by their geometries and couplings, the quantification of an offset between the mode and electrostatic centers, and the reduction of the cavity shift uncertainty to sub-dominant levels. Measuring g at four magnetic fields with cavity shifts spanning thirty times the final g-value uncertainty provides a check on the calculated cavity shifts. Magnetic field fluctuations limit the measurement of g by adding a noise-model dependence to the extraction of the cyclotron and anomaly frequencies from their resonance lines; the relative agreement of two line-splitting methods quantifies a lineshape model uncertainty. New techniques promise to increase field stability, narrow the resonance lines, and accelerate the measurement cycle. The measured g allows tests for physics beyond the Standard Model through searches for its temporal variation and comparisons with a “theoretical” g-value calculated from quantum electrodynamics and an independently measured fine structure constant.

•Jan 1, 2007•0 citations

Microwave-cavity modes directly observed in a Penning trap

Robert S. Van Dyck, Fred L. Moore, Dean L. Farnham +2 more

The microwave-cavity mode pattern has been directly observed in an old-style compensated Penning trap by a simple bolometric technique which monitors changes in the temperature of the axial center-of-mass motion for a cloud of electrons. The method allows one to easily determine the position of individual modes to a precision better than 0.01%. Presently, over 60 modes have been observed for fields between 17 and 60 kG and an upper limit estimate of 2300 has been made for the cavity Q.

Physical Review A•Oct 1, 1987•13 citations
A spherical Penning trap has well-separated, clean microwave resonances, making it attractive for precision measurements of the electron magnetic moment and for dark-photon and axion searches with trapped electrons. We demonstrate single-electron trapping in a spherical Penning trap and characterize its microwave resonance structure. The design, single-electron detection, microwave mode characterization, and advantages of this geometry are presented.
We investigate theoretically the use of an electron in a Penning trap as a detector of single microwave photons. At the University of Sussex we are developing a chip Penning trap technology, designed to be integrated within quantum circuits. Microwave photons are guided into the trap and interact with the electron’s quantum cyclotron motion. This is an electric dipole transition, where the near field of the microwave radiation induces quantum jumps of the cyclotron harmonic oscillator. The quantum jumps can be monitored using the continuous Stern-Gerlach effect, providing the quantum non demolition signal of the microwave quanta. We calculate the quantum efficiency of photon detection and discuss the main features and technical challenges for the trapped electron as a quantum microwave sensor.
A cylindrical Penning trap is of such high quality that a single electron is observed with good signal-to-noise. The trap is also a good approximation to an ideal cylindrical microwave cavity. This is documented in situ at 4 K with a new probe utilizing trapped electrons. An extraordinary control of the cavity-electron interaction results and opens the way to a new generation of electron magnetic moment measurements, not limited by either cavity frequency shifts or damping widths, and to sideband cooling of an electron motion to very low (mK) temperatures.
We propose a scheme for quantum-logic spectroscopy of an electron or positron in a Penning trap. An electron or positron in a spectroscopy trap is coupled to a remote logic electron or positron via a wire to achieve motional entanglement. By separating the two traps, one can significantly improve magnetic field homogeneity, microwave characteristics, and detection sensitivity. The proposed scheme will improve the measurement precision of the electron's and positron's magnetic moments and charge-to-mass ratios, enabling precise tests of the standard model of particle physics.
A single electron in a quantum cyclotron yields new measurements of the electron magnetic moment, given by g/2 = 1.00115965218073(28)[0.28 ppt], and the fine structure constant, α −1 = 137.035999084(51)[0.37 ppb], both significantly improved from prior results. The static magnetic and electric fields of a Penning trap confine the electron, and a 100 mK dilution refrigerator cools its cyclotron motion to the quantum-mechanical ground state. A quantum nondemolition measurement allows resolution of single cyclotron jumps and spin flips by coupling the cyclotron and spin energies to the frequency of the axial motion, which is self-excited and detected with a cryogenic amplifier. The trap electrodes form a high-Q microwave resonator near the cyclotron frequency; coupling between the cyclotron motion and cavity modes can inhibit spontaneous emission by over 100 timesthe free-space rate and shiftthe cyclotron frequency, a systematic effect that dominated the uncertainties of previous g-value measurements. A cylindrical trap geometry creates cavity modes with analytically calculable couplingsto cyclotron motion. Two independent methods use the cyclotron damping rate of an electron plasma or of the single electron itself as probes of the cavity mode structure and allow the identification ofthe modes by their geometries and couplings, the quantification of an offset between the mode and electrostatic centers, and the reduction of the cavity shift uncertainty to sub-dominant levels. Measuring g at four magnetic fields with cavity shifts spanning thirty times the final g-value uncertainty provides a check on the calculated cavity shifts. Magnetic field fluctuations limit the measurement of g by adding a noise-model dependence to the extraction of the cyclotron and anomaly frequencies from their resonance lines; the relative agreement of two line-splitting methods quantifies a lineshape model uncertainty. New techniques promise to increase field stability, narrow the resonance lines, and accelerate the measurement cycle. The measured g allows tests for physics beyond the Standard Model through searches for its temporal variation and comparisons with a “theoretical” g-value calculated from quantum electrodynamics and an independently measured fine structure constant.