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Atomic Parity Nonconservation Experiment

Pintu Mandal

Published Mar 18, 2014• 0 citations
OpenAlex

Abstract

Motivated by the challenges and limitation of existing experimental techniques, this work elaborates our recent proposal for the precision measurement of atomic parity nonconservation by quantum metrology with an entangled pair of trapped ions. Although the technique is fundamentally based on an existing proposal, it can potentially reach a figure of merit twice as high for an exceedingly tiny observable, yet to be measured in any ion trap experiment. The systematic of the technique have been shown to be better controlled as compared to other experiments. Since the goal of the experiment is to test the Standard Model of physics, the measured parity violating transitional dipole matrix element has to be compared with the theory of competitive precision. The choice of the element therefore plays an important role for the success of the experiment. Barium and radium ions have been compared from this perspective. The work presents the theoretical study on nuclear spin dependent atomic parity nonconservation and nuclear anapole moment in different isotopes of these ions and proposes specific transitions that are experimentally feasible.

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Motivated by the challenges and limitation of existing experimental techniques, this work elaborates our recent proposal for the precision measurement of atomic parity nonconservation by quantum metrology with an entangled pair of trapped ions. Although the technique is fundamentally based on an existing proposal, it can potentially reach a figure of merit twice as high for an exceedingly tiny observable, yet to be measured in any ion trap experiment. The systematic of the technique have been shown to be better controlled as compared to other experiments. Since the goal of the experiment is to test the Standard Model of physics, the measured parity violating transitional dipole matrix element has to be compared with the theory of competitive precision. The choice of the element therefore plays an important role for the success of the experiment. Barium and radium ions have been compared from this perspective. The work presents the theoretical study on nuclear spin dependent atomic parity nonconservation and nuclear anapole moment in different isotopes of these ions and proposes specific transitions that are experimentally feasible.
An entangled state prepared in a decoherence-free subspace, together with a Ramsey-type measurement, can probe parity violation in heavy alkali-metal ions such as Ba+{}^{+}+ or Ra+{}^{+}+. Here we propose an experiment with Ba+{}^{+}+ as an example to measure the small parity-violating effect in this system. It has been shown that a measurement on a maximally correlated system will reduce the uncertainty as compared to that on a single ion measurement, and also provides a feasible solution to measure the nuclear-spin-dependent part of the total parity-violating light shift in an ionic system.
Atomic parity violation (APV) provides a low-energy probe of the weak interaction between electrons and nuclei, complementary to collider tests of the Standard Model. Isotope-chain measurements are especially attractive because they test weak-charge scaling while reducing dependence on absolute atomic-structure theory. We review the APV mechanism, the state of the art in Cs and Yb, and recent trapped-ion, optical-lattice, and molecular proposals. Motivated by progress in coherent control of atoms, ions, and molecules, we ask a metrological question: given N probes distributed over an isotope chain, what quantum strategy optimally measures a deviation from Standard Model weak-charge scaling? The optimum is a particular form of a cross-isotope cat state protocol. We compare this protocol with the standard quantum limit, squeezed-array, same-isotope cat, and discuss extension to recently suggested decoherence-free subspace protocols. We show that entanglement can strongly accelerate statistical averaging, but the ultimate precision is set by APV-specific systematic floors which require careful studies.
Weak interactions within a nucleus generate a nuclear spin dependent, parity-violating electromagnetic moment, the anapole moment. We analyze a method to measure the nuclear anapole moment through the electric dipole transition it induces between hyperfine states of the ground level. The method requires tight confinement of the atoms to position them at the antinode of a standing wave Fabry-Perot cavity driving the anapole-induced microwave E1E1E1 transition. We explore the necessary limits in the number of atoms, excitation fields, trap type, interrogation method, and systematic tests necessary for such measurements in francium, the heaviest alkali.
Quantum technologies exploit entanglement to revolutionize computing, measurement, and communication. This has stimulated the research in different areas of physics to engineer and manipulate fragile many-particle entangled states. Progress has been particularly rapid for atoms. Thanks to the large and tunable nonlinearities and the well developed techniques for trapping, controlling and counting, many groundbreaking experiments have demonstrated the generation of entangled states of trapped ions, cold and ultracold gases of neutral atoms. Moreover, atoms can couple strongly to external forces and light fields, which makes them ideal for ultra-precise sensing and time keeping. All these factors call for generating non-classical atomic states designed for phase estimation in atomic clocks and atom interferometers, exploiting many-body entanglement to increase the sensitivity of precision measurements. The goal of this article is to review and illustrate successful theoretical proposals and experiments with atomic ensembles that have demonstrated many-particle entanglement and quantum-enhanced metrology.
This paper presents an experimental platform designed to facilitate quantum logic control of polar molecular ions in a segmented ring ion trap, paving the way for precision measurements. This approach focuses on achieving near-unity state preparation and detection, as well as long spin-precession coherence. A distinctive aspect lies in separating state preparation and detection conducted in a static frame from parity-selective spin precession in a rotating frame. Moreover, the method is designed to support spatially and temporally coincident measurements on multiple ions prepared in states with different sensitivity to the new physics of interest. This provides powerful techniques to probe and minimize potential sources of systematic error. While the primary focus of this paper is on detecting the electron's electric dipole moment (eEDM) using 232ThF+^{232}\mathrm{ThF}^{+}232ThF+ ions, the proposed methodology holds promise for broader applications, particularly with ion species that exhibit enhanced sensitivity to the nuclear magnetic quadruple moment (nMQM).
Building robust instruments capable ofmaking interferometric measurements with precision beyond the standard quantum limit remains an important goal in many metrology laboratories. We describe here the basic concepts underlying spin squeezing experiments that allow one to surpass this limit. In principle it is possible to reach the so-called Heisenberg limit, which constitutes an improvement in precision by a factorv N, where N is the number of particles on which the measurement is carried out. In particular, we focus on recent progress toward implementing spin squeezing with a cloud of beryllium ions in a Penning ion trap, via the geometric phase gate used more commonly for performing two-qubit entangling operations in quantum computing experiments.