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J. -Ph. Karr

Publications and source records attributed to J. -Ph. Karr.

11 recordsLinked to original sources
arXiv2026

Spectroscopy of the Hyperfine Structure of HD$^+$ in Rotationally Excited States with 10-ppb Uncertainty

We report the first measurement of the total hyperfine interval in the manifold of the ($v=0,L=3$) rovibrational state of HD$^+$ using microwave spectroscopy of HD$^+$ ions in a linear Paul trap. To overcome the low (0.2%) occupancy of the quantum states involved, we employ a novel technique that combines intermittent Majorana depolarization of the HD$^+$ ensemble with redistribution of rotational-state population by blackbody radiation to effectively amplify the occupancy by a factor of 25. This enables the observation of a single field-insensitive magnetic subcomponent of the hyperfine transition, leading to a measured total hyperfine interval of ${1\,050\,804.511}\pm 0.011\,$kHz with an unprecedented relative uncertainty of 10 parts per billion. This differs from the theoretically predicted value ${1\,050\,802.78}\pm 0.89\,$kHz by 1.9$σ$. We show that our experimental value is consistent with the recently measured hyperfine structure of the ($v=0,L=0$) rovibrational state of HD$^+$ [C.M. König et al., High-precision Penning trap spectroscopy of the ground state spin structure of HD$^+$, Phys. Rev. Lett. $\mathbf{136}$,143002 (2026)], for which a similar deviation from theory was found. Our work may help resolve puzzling discrepancies between the theoretical and experimental hyperfine structure observed previously in optical rovibrational spectra of HD$^+$.

physics.atom-ph↗
arXiv2025

Quantum Computing Approach to Atomic and Molecular Three-Body Systems

We present high-precision quantum computing simulations of three-body atoms (He, H$^-$) and molecules (H$_2^+$, HD$^+$), the latter being studied beyond the Born-Oppenheimer approximation. The Non-Iterative Disentangled Unitary Coupled Cluster Variational Quantum Eigensolver (NI-DUCC-VQE) [M. Haidar et al., Quantum Sci. Technol. 10, 025031 (2025)] is used. By combining a first-quantized Hamiltonian with a Minimal Complete Pool (MCP) of Lie-algebraic excitations, we construct a compact ansatz with a gradient-independent construction, avoiding costly gradient evaluations and yielding efficient computational scaling with both basis size and electron number. It avoids barren plateaus and enables rapid convergence, achieving energy errors as low as 10$^{-11}$ a.u. with state fidelities only limited by arithmetic precision in only a few thousand function evaluations in all four systems. These results make three-body atoms and molecules excellent candidates for benchmarking and testing on current Noisy Intermediate-Scale Quantum (NISQ) devices. Further, our approach can be extended to more complex systems with larger basis sets, taking advantage of the efficient scaling of qubit requirements to study electronic correlations and non-adiabatic effects with high precision. We also demonstrate the applicability of NI-DUCC-VQE for simulating higher-order effects such as relativistic corrections and hyperfine interactions.

quant-ph↗
arXiv2022

Proton-Electron Mass Ratio from Laser Spectroscopy of HD$^+$ at the Part-Per-Trillion Level

Accepted values of the masses of several subatomic particles have been under debate since recent measurements in Penning traps produced more precise yet incompatible results, implying possible inconsistencies in closely related physical constants like the proton-electron and deuteron-proton mass ratios. These quantities also influence the predicted vibrational spectrum of the deuterated molecular hydrogen ion in its electronic ground state, of which we measured the v=0 - 9 overtone transition frequency with an uncertainty of 2.9 parts-per-trillion through Doppler-free two-photon laser spectroscopy. Leveraging high-precision ab initio calculations we convert our measurement to tight constraints on the proton-electron and deuteron-proton mass ratios, consistent with the most recent Penning-trap determinations of these quantities, and yielding a new value of the proton-electron mass ratio with an unprecedented precision of 21 parts-per-trillion.

physics.atom-ph↗
arXiv2017

Proton-electron mass ratio from HD$^+$ revisited

We present a new derivation of the proton-electron mass ratio from the hydrogen molecular ion, HD$^+$. The derivation entails the adjustment of the mass ratio in highly precise theory so as to reproduce accurately measured ro-vibrational frequencies. This work is motivated by recent improvements of the theory, as well as the more accurate value of the electron mass in the recently published CODATA-14 set of fundamental constants, which justifies using it as input data in the adjustment, rather than the proton mass value as done in previous works. This leads to significantly different sensitivity coefficients and, consequently, a different value and larger uncertainty margin of the proton-electron mass ratio as obtained from HD$^+$.

physics.atom-ph↗
arXiv2017

One-loop vacuum polarization at m$α$7 and higher orders for three-body molecular systems

We present calculations of the one-loop vacuum polarization correction (Uehling potential) for the three-body problem in the NRQED formalism. The case of one-electron molecular systems is considered. Numerical results of the vacuum polarization contribution at m$α$7 and higher orders for the fundamental transitions (v = 0, L = 0) $\rightarrow$ (v ' = 1, L ' = 0) in the H2+ and HD+ molecular ions are presented and compared with calculations performed in the adiabatic approximation. The residual uncertainty from this contribution on the transition frequencies is shown to be of a few tens of Hz.

physics.atom-ph↗
arXiv2016

High-precision spectroscopy of the HD+ molecule at the 1-p.p.b. level

Recently we reported a high precision optical frequency measurement of the (v,L):(0,2)->(8,3) vibrational overtone transition in trapped deuterated molecular hydrogen (HD+) ions at 10 mK temperature. Achieving a resolution of 0.85 parts-per-billion (p.p.b.) we found the experimental value ($ν_0= 383,407,177.38(41)$ MHz) to be in agreement with the value from molecular theory ($ν_\text{th}=383,407,177.150(15)$ MHz) within 0.6(1.1) p.p.b. [Biesheuvel et al., Nat. Commun. 7, 10385 (2016)]. This enabled an improved test of molecular theory (including QED), new constraints on the size of possible effects due to 'new physics', and the first determination of the proton-electron mass ratio from a molecule. Here, we provide the details of the experimental procedure, spectral analysis, and the assessment of systematic frequency shifts. Our analysis focuses in particular on deviations of the HD+ velocity distribution from thermal (Gaussian) distributions under the influence of collisions with fast ions produced during (laser-induced) chemical reactions, as such deviations turn out to significantly shift the hyperfine-less vibrational frequency as inferred from the saturated and Doppler-broadened spectrum, which contains partly unresolved hyperfine structure.

physics.atom-ph↗
arXiv2016

Probing QED and fundamental constants through laser spectroscopy of vibrational transitions in HD+

The simplest molecules in nature, molecular hydrogen ions in the form of H2+ and HD+, provide an important benchmark system for tests of quantum electrodynamics in complex forms of matter. Here, we report on such a test based on a frequency measurement of a vibrational overtone transition in HD+ by laser spectroscopy. We find that the theoretical and experimental frequencies are equal to within 0.6(1.1) parts per billion, which represents the most stringent test of molecular theory so far. Our measurement not only confirms the validity of high-order quantum electrodynamics in molecules, but also enables the long predicted determination of the proton-to-electron mass ratio from a molecular system, as well as improved constraints on hypothetical fifth forces and compactified higher dimensions at the molecular scale. With the perspective of comparisons between theory and experiment at the 0.01 part-per-billion level, our work demonstrates the potential of molecular hydrogen ions as a probe of fundamental physical constants and laws.

physics.atom-ph↗
arXiv2014

One-loop vacuum polarization at $mα^7$ order for the two center problem

We present calculations of the one-loop vacuum polarization contribution (Uehling potential) for the two-center problem in the NRQED formalism. The cases of hydrogen molecular ions ($Z_1=Z_2=1$) as well as antiprotonic helium ($Z_1=2$, $Z_2=-1$) are considered. Numerical results of the vacuum polarization contribution at $mα^7$ order for the fundamental transitions $(v=0,L=0)\to(v'=1,L'=0)$ in H$_2^+$ and HD$^+$ are presented.

physics.atom-ph↗
arXiv2004

Optical bistability in semiconductor microcavities in the nondegenerate parametric oscillation regime: analogy with the optical parametric oscillator

We report the observation of optical bistability in a microcavity pumped at the "magic angle". Experimental evidence is given in the form of a hysteresis cycle of the nonlinear emission as a function of the pump intensity or the position of the excitation spot. The results can be well understood with simple theoretical considerations that underline the fundamental analogy between our system and an optical parametric oscillator.

cond-mat.str-el↗