arXiv subjects

Richard Hobson

Publications and source records attributed to Richard Hobson.

16 recordsLinked to original sources

arXiv2026

Technical Proposal for the Atom Interferometer CERN Experiment (AICE) Facility

We present the technical proposal for the Atom Interferometer CERN Experiment (AICE), a $\mathcal{O}(100)$ m vertical atom interferometer to be installed against the wall of the PX46 access shaft to the LHC. AICE is conceived as a versatile and flexible long-baseline atom-interferometry facility whose primary scientific goal is probing for bosonic ultralight dark matter (ULDM) in a mass range inaccessible to other experiments, with a secondary goal of pioneering the exploration of gravitational waves (GWs) with frequencies in the range ${\sim}$0.03-3 Hz as a pathfinder for future longer-baseline detectors. The initial configuration employs ultracold $^{87}$Sr atoms in a single-photon 698-nm interferometer with three shaft-based atom sources in a multi-source gradiometer geometry, supported by one surface reference source for laser stabilisation and diagnostics, to target scalar ULDM. Operation with $^{88}$Sr will give sensitivity to axion-like particles (ALPs), vector ULDM with $B-L$ couplings and violation of the principle of equivalence, while a $^{171}$Yb upgrade will improve the sensitivity to $B-L$ couplings and equivalence violations. Probing the Einstein equivalence principle (EP) and measuring $\alpha$ will proceed in parallel with the ULDM searches. A conceptual feasibility study and a detailed technical implementation study have established that PX46 is a uniquely mature and implementation-ready site, with no technical showstoppers. Completing site preparation works during LS3 would enable the subsequent installation and operation of AICE without impacting HL-LHC operations. The detector design builds on the VLBAI and MAGIS experiments and the AION-10 Technical Design Report, scaling the strontium gradiometer architecture to the $\sim$100 m baseline. AICE is endorsed by the TVLBAI Proto-Collaboration, comprising 57 institutions in 22 countries.

hep-ex↗

arXiv2026

A High-Flux Source of Cold Strontium with a Loading Rate of $4 \times 10^{10}$ atoms/s for Open Release

We present a high-flux source of cold strontium atoms based on a two-dimensional magneto-optical trap (2D MOT) and a Zeeman slower. We use the source to load a 3D MOT in a separate science chamber, observing a loading rate of $4 \times 10^{10}$ atoms/s -- to our knowledge, the highest reported loading flux for strontium. To characterise the vacuum pressure in the science chamber, we load the atoms into a magnetic trap and measure a lifetime of between 8 and 24 seconds, depending on oven temperature. Finally, we characterise the atom flux and velocity distributions from the oven and from the 2D MOT source, finding reasonable agreement with models in the free molecular flow regime. Our results show it is possible to readily produce a cold strontium flux at comparable levels to alkali species, at oven temperatures compatible with long-term operation, and at vacuum pressures suitable for state-of-the-art quantum experiments. We make our design available at no cost, to benefit researchers in the quantum community.

cond-mat.quant-gas↗

arXiv2025

Letter of Intent: AICE -- 100m Atom Interferometer Experiment at CERN

We propose an O(100)m Atom Interferometer (AI) experiment -- AICE -- to be installed against a wall of the PX46 access shaft to the LHC. This experiment would probe unexplored ranges of the possible couplings of bosonic ultralight dark matter (ULDM) to atomic constituents and undertake a pioneering search for gravitational waves (GWs) at frequencies intermediate between those to which existing and planned experiments are sensitive, among other fundamental physics studies. A conceptual feasibility study showed that this AI experiment could be isolated from the LHC by installing a shielding wall in the TX46 gallery, and surveyed issues related to the proximity of the LHC machine, finding no technical obstacles. A detailed technical implementation study has shown that the preparatory civil-engineering work, installation of bespoke radiation shielding, deployment of access-control systems and safety alarms, and installation of an elevator platform could be carried out during LS3, allowing installation and operation of the AICE detector to proceed during Run 4 without impacting HL-LHC operation. These studies have established that PX46 is a uniquely promising location for an AI experiment. We foresee that, if the CERN management encourages this Letter of Intent, a significant fraction of the Terrestrial Very Long Baseline Atom Interferometer (TVLBAI) Proto-Collaboration may wish to contribute to AICE.

hep-ex↗

arXiv2025

Prospects for detecting new dark physics with the next generation of atomic clocks

Wide classes of new fundamental physics theories cause apparent variations in particle mass ratios in space and time. In theories that violate the weak equivalence principle (EP), those variations are not uniform across all particles and may be detected with atomic and molecular clock frequency comparisons. In this work we explore the potential to detect those variations with near-future clock comparisons. We begin by searching published clock data for variations in the electron-proton mass ratio. We then undertake a statistical analysis to model the noise in a variety of clock pairs that can be built in the near future according to the current state of the art, determining their sensitivity to various fundamental physics signals. Those signals are then connected to constraints on fundamental physics theories that lead directly or indirectly to an effective EP-violating, including those motivated by dark matter, dark energy, the vacuum energy problem, unification or other open questions of fundamental physics. This work results in projections for tight new bounds on fundamental physics that could be achieved with atomic and molecular clocks within the next few years. Our code for this work is packaged into a forecast tool that translates clock characteristics into bounds on fundamental physics.

hep-ph↗

arXiv2023

Analysis of atomic-clock data to constrain variations of fundamental constants

We present a new framework to study the time variation of fundamental constants in a model-independent way. Model independence implies more free parameters than assumed in previous studies. Using data from atomic clocks based on $^{87}$Sr, $^{171}$Yb$^+$ and $^{133}$Cs, we set bounds on parameters controlling the variation of the fine-structure constant, $α$, and the electron-to-proton mass ratio, $μ$. We consider variations on timescales ranging from a minute to almost a day. In addition, we use our results to derive some of the tightest limits to date on the parameter space of models of ultralight dark matter and axion-like particles.

physics.atom-ph↗

arXiv2020

Improving the Q factor of an optical atomic clock using quantum non-demolition measurement

Quantum non-demolition (QND) measurement is a remarkable tool for the manipulation of quantum systems. It allows specific information to be extracted while still preserving fragile quantum observables of the system. Here we apply cavity-based QND measurement to an optical lattice clock---a type of atomic clock with unrivalled frequency precision---preserving the quantum coherence of the atoms after readout with 80\% fidelity. We apply this technique to stabilise the phase of an ultrastable laser to a coherent atomic state via a series of repeated QND measurements. We exploit the improved phase-coherence of the ultrastable laser to interrogate a separate optical lattice clock, using a Ramsey spectroscopy time extended from 300~ms to 2~s. With this technique we maintain 95\% contrast and observe a seven-fold increase in the clock's \emph{Q} factor to $1.7\times10^{15}$.

physics.atom-ph↗

arXiv2020

A strontium optical lattice clock with $1 \times 10^{-17}$ uncertainty and measurement of its absolute frequency

We present a measurement of the absolute frequency of the 5s$^2$ $^1$S$_0$ to 5s5p $^3$P$_0$ transition in $^{87}$Sr, which is a secondary representation of the SI second. We describe the optical lattice clock apparatus used for the measurement, and we focus in detail on how its systematic frequency shifts are evaluated with a total fractional uncertainty of $1 \times 10^{-17}$. Traceability to the International System of Units is provided via comparison to International Atomic Time (TAI). Gathering data over 5- and 15-day periods, with the lattice clock operating on average 74$\%$ of the time, we measure the frequency of the transition to be 429228004229873.1(5) Hz, which corresponds to a fractional uncertainty of $1 \times 10^{-15}$. We describe in detail how this uncertainty arises from the intermediate steps linking the optical frequency standard, through our local time scale UTC(NPL), to an ensemble of primary and secondary frequency standards which steer TAI. The calculated absolute frequency of the transition is in good agreement with recent measurements carried out in other laboratories around the world.

physics.atom-ph↗

arXiv2020

A mid-infrared magneto-optical trap of metastable strontium for an optical lattice clock

We report on the realization of a magneto-optical trap (MOT) for metastable strontium operating on the 2.92 $μ$m transition between the energy levels $5s5p~^3\mathrm{P}_2$ and $5s4d~^3\mathrm{D}_3$. The strontium atoms are initially captured in a MOT operating on the 461 nm transition between the energy levels $5s^2~^1\mathrm{S}_0$ and $5s5p~^1\mathrm{P}_1$, prior to being transferred into the metastable MOT and cooled to a final temperature of 6 $μ$K. Challenges arising from aligning the mid-infrared and 461 nm light are mitigated by employing the same pyramid reflector to realize both MOTs. Finally, the 2.92 $μ$m transition is used to realize a full cooling sequence for an optical lattice clock, in which cold samples of $^{87}\mathrm{Sr}$ are loaded into a magic-wavelength optical lattice and initialized in a spin-polarized state to allow high-precision spectroscopy of the $5s^2~^1\mathrm{S}_0$ to $5s5p~^3\mathrm{P}_0$ clock transition.

physics.atom-ph↗

arXiv2019

Cavity-enhanced non-destructive detection of atoms for an optical lattice clock

We demonstrate a new method of cavity-enhanced non-destructive detection of atoms for a strontium optical lattice clock. The detection scheme is shown to be linear in atom number up to at least 10,000 atoms, to reject technical noise sources, to achieve signal to noise ratio close to the photon shot noise limit, to provide spatially uniform atom-cavity coupling, and to minimize inhomogeneous ac Stark shifts. These features enable detection of atoms with minimal perturbation to the atomic state, a critical step towards realizing an ultra-high-stability, quantum-enhanced optical lattice clock.

physics.atom-ph↗

arXiv2019

Dynamic decoupling of laser phase noise in compound atomic clocks

The frequency stability achieved by an optical atomic clock ultimately depends on the coherence of its local oscillator. Even the best ultrastable lasers only allow interrogation times of a few seconds, at present. Here we present a universal measurement protocol that overcomes this limitation. Engineered dynamic decoupling of laser phase noise allows any optical atomic clock with high signal-to-noise ratio in a single interrogation to reconstruct the laser's phase well beyond its coherence limit. A compound clock is then formed in combination with another optical clock of any type, allowing the latter to achieve significantly higher frequency stability than on its own. We demonstrate implementation of the protocol in a realistic proof-of-principle experiment with a phase reconstruction fidelity of 99 %. The protocol enables minute-long interrogation for the best ultrastable laser systems. Likewise, it can improve clock performance where less stable local oscillators are used, such as in transortable systems.

physics.atom-ph↗

arXiv2019

A low-noise resonant input transimpedance amplified photodetector

We present the design and characterisation of a low-noise, resonant input transimpedance amplified photodetector. The device operates at a resonance frequency of $90 \,\textrm{MHz}$ and exhibits an input referred current noise of $1.2\,\textrm{pA}/\sqrt{\textrm{Hz}}$---marginally above the the theoretical limit of $1.0\,\textrm{pA}/\sqrt{\textrm{Hz}}$ set by the room temperature Johnson noise of the detector's $16\,\textrm{k}Ω$ transimpedance. As a result, the photodetector allows for shot-noise limited operation for input powers exceeding $14\,μ\textrm{W}$ at $461\,\textrm{nm}$ corresponding to a noise equivalent power of $3.5\,\textrm{pW}/\sqrt{\textrm{Hz}}$. The key design feature which enables this performance is a low-noise, common-source JFET amplifier at the input which helps to reduce the input referred noise contribution of the following amplification stages.

physics.ins-det↗

arXiv2019

AEDGE: Atomic Experiment for Dark Matter and Gravity Exploration in Space

We propose in this White Paper a concept for a space experiment using cold atoms to search for ultra-light dark matter, and to detect gravitational waves in the frequency range between the most sensitive ranges of LISA and the terrestrial LIGO/Virgo/KAGRA/INDIGO experiments. This interdisciplinary experiment, called Atomic Experiment for Dark Matter and Gravity Exploration (AEDGE), will also complement other planned searches for dark matter, and exploit synergies with other gravitational wave detectors. We give examples of the extended range of sensitivity to ultra-light dark matter offered by AEDGE, and how its gravitational-wave measurements could explore the assembly of super-massive black holes, first-order phase transitions in the early universe and cosmic strings. AEDGE will be based upon technologies now being developed for terrestrial experiments using cold atoms, and will benefit from the space experience obtained with, e.g., LISA and cold atom experiments in microgravity. This paper is based on a submission (v1) in response to the Call for White Papers for the Voyage 2050 long-term plan in the ESA Science Programme. ESA limited the number of White Paper authors to 30. However, in this version (v2) we have welcomed as supporting authors participants in the Workshop on Atomic Experiments for Dark Matter and Gravity Exploration held at CERN: ({\tt https://indico.cern.ch/event/830432/}), as well as other interested scientists, and have incorporated additional material.

gr-qc↗

arXiv2019

Guidelines for developing optical clocks with $10^{-18}$ fractional frequency uncertainty

There has been tremendous progress in the performance of optical frequency standards since the first proposals to carry out precision spectroscopy on trapped, single ions in the 1970s. The estimated fractional frequency uncertainty of today's leading optical standards is currently in the $10^{-18}$ range, approximately two orders of magnitude better than that of the best caesium primary frequency standards. This exceptional accuracy and stability is resulting in a growing number of research groups developing optical clocks. While good review papers covering the topic already exist, more practical guidelines are needed as a complement. The purpose of this document is therefore to provide technical guidance for researchers starting in the field of optical clocks. The target audience includes national metrology institutes (NMIs) wanting to set up optical clocks (or subsystems thereof) and PhD students and postdocs entering the field. Another potential audience is academic groups with experience in atomic physics and atom or ion trapping, but with less experience of time and frequency metrology and optical clock requirements. These guidelines have arisen from the scope of the EMPIR project "Optical clocks with $1 \times 10^{-18}$ uncertainty" (OC18). Therefore, the examples are from European laboratories even though similar work is carried out all over the world. The goal of OC18 was to push the development of optical clocks by improving each of the necessary subsystems: ultrastable lasers, neutral-atom and single-ion traps, and interrogation techniques. This document shares the knowledge acquired by the OC18 project consortium and gives practical guidance on each of these aspects.

physics.atom-ph↗

arXiv2019

A pyramid MOT with integrated optical cavities as a cold atom platform for an optical lattice clock

We realize a two-stage, hexagonal pyramid magneto-optical trap (MOT) with strontium, and demonstrate loading of cold atoms into cavity-enhanced 1D and 2D optical lattice traps, all within a single compact assembly of in-vacuum optics. We show that the device is suitable for high-performance quantum technologies, focusing especially on its intended application as a strontium optical lattice clock. We prepare $2\times 10^4$ spin-polarized atoms of $^{87}$Sr in the optical lattice within 500 ms; we observe a vacuum-limited lifetime of atoms in the lattice of 27 s; and we measure a background DC electric field of 12 Vm$^{-1}$ from stray charges, corresponding to a fractional frequency shift of $(-1.2\times 0.8)\times 10^{-18}$ to the strontium clock transition. When used in combination with careful management of the blackbody radiation environment, the device shows potential as a platform for realizing a compact, robust, transportable optical lattice clock with systematic uncertainty at the $10^{-18}$ level.

physics.atom-ph↗

arXiv2017

Rydberg Electrometry for Optical Lattice Clocks

Electrometry is performed using Rydberg states to evaluate the quadratic Stark shift of the $5s^2$ $^1\textrm{S}_0-5s5p$ $^3\textrm{P}_0$ clock transition in strontium. By measuring the Stark shift of the highly excited $5s75d\;^1\textrm{D}_2$ state using electromagnetically induced transparency, we characterize the electric field with sufficient precision to provide tight constraints on the systematic shift to the clock transition. Using the theoretically derived, and experimentally verified, polarizability for this Rydberg state we can measure the residual field with an uncertainty well below $1 \textrm{V} \textrm{m}^{-1}$. This resolution allows us to constrain the fractional frequency uncertainty of the quadratic Stark shift of the clock transition to $2\times10^{-20}$.

physics.atom-ph↗

arXiv2016

A low maintenance Sr optical lattice clock

We describe the Sr optical lattice clock apparatus at NPL with particular emphasis on techniques used to increase reliability and minimise the human requirement in its operation. Central to this is a clock-referenced transfer cavity scheme for the stabilisation of cooling and trapping lasers. We highlight several measures to increase the reliability of the clock with a view towards the realisation of an optical time-scale. The clock contributed 502 hours of data over a 25 day period (84% uptime) in a recent measurement campaign with several uninterrupted periods of more than 48 hours. An instability of $2\times10^{-17}$ was reached after $10^5$ s of averaging in an interleaved self-comparison of the clock.

physics.atom-ph↗