arXiv subjects

Matthew Chilcott

Publications and source records attributed to Matthew Chilcott.

9 recordsLinked to original sources

arXiv2026

Quantum-enabled complete RF-polarimetry with an optically-wired atomic sensor

Rydberg atomic electrometry leverages the extreme sensitivity of highly excited atoms for calibration-free electric field measurements. The technique uses a non-metallic vapor cell to link properties of an RF field to a spectroscopic readout in the optical domain. Most demonstrations have so far focused on detecting linearly-polarized fields, for which the induced splitting of dressed atomic levels is rotationally invariant. Here we report on Rydberg atomic measurements of RF fields in a general state of polarization (SOP) which we map onto the Poincar\'{e} sphere through spectroscopic fingerprints. For a Stokes vector circumnavigating a Poincar\'e sphere meridian, we witness a continuous transformation of the atomic eigenenergy spectrum. Because the relative positions of eigenenergies are locked in place by quantization of angular momentum, the framework is universal and calibration free. We provide a specific demonstration in rubidium, which generalizes to all systems with a single valence electron.

quant-ph↗

arXiv2025

EIT Spectroscopy of Rydberg Levels Dressed by Linearly Polarized RF fields: Complementary Angular Response for Two Types of Transition Ladders

Rydberg atoms efficiently link photons between the radio-frequency (RF) and optical domains. They furnish a medium in which the presence of an RF-field imprints on the transmission of a probe laser beam by altering the coherent coupling between atomic quantum states. The immutable atomic energy structure underpins quantum-metrological RF-field measurements and has driven intensive efforts to realize inherently self-calibrated sensing devices. Here we investigate spectroscopic signatures owing to the quantization of atomic angular momentum. Using an electromagnetically-induced transparency (EIT) sensing scheme, specific combinations of atomic terms are shown to give rise to universal, distinctive fingerprints in the detected optical fields upon rotating a linearly polarized RF field. Employing a dressed state picture, we identify two types of atomic angular momentum ladders that display strikingly disparate spectroscopic characteristics, including the distinctive absence or presence of a central spectral EIT peak. Our study adds important insights into the prospects of Rydberg atomic gases for quantum metrological electric field characterization including polarimetry. In particular, it calls into question prevailing interpretations of SI-traceable Rydberg atom electrometers.

quant-ph↗

arXiv2024

Observing S-Matrix Pole Flow in Resonance Interplay: Cold Collisions of Ultracold Atoms in a Miniature Laser-based Accelerator

We provide an overview of experiments exploring resonances in the collision of ultracold clouds of atoms. Using a laser-based accelerator that capitalizes on the energy resolution provided by the ultracold atomic setting, we unveil resonance phenomena such as Feshbach and shape resonances in their quintessential form by literally photographing the halo of outgoing scattered atoms. We exploit the tunability of magnetic Feshbach resonances to instigate an interplay between scattering resonances. By experimentally recording the scattering in a parameter space spanned by collision energy and magnetic field, we capture the imprint of the $S$-matrix pole flow in the complex energy plane. After revisiting experiments that place a Feshbach resonance in the proximity of a shape resonance and an anti-bound state, respectively, we discuss the possibility of using $S$-matrix pole interplay between two Feshbach resonances to create a bound-state-in-the-continuum.

cond-mat.quant-gas↗

arXiv2021

Microscopy of an ultranarrow Feshbach resonance using a laser-based atom collider: A quantum defect theory analysis

We employ a quantum defect theory framework to provide a detailed analysis of the interplay between a magnetic Feshbach resonance and a shape resonance in cold collisions of ultracold $\rm ^{87}Rb$ atoms as captured in recent experiments using a laser-based collider [Phys. Rev. Research 3, 033209 (2021)]. By exerting control over a parameter space spanned by both collision energy and magnetic field, the width of a Feshbach resonance can be tuned over several orders of magnitude. We apply a quantum defect theory specialized for ultracold atomic collisions to fully describe of the experimental observations. While the width of a Feshbach resonance generally increases with collision energy, its coincidence with a shape resonance leads to a significant additional boost. By conducting experiments at a collision energy matching the shape resonance and using the shape resonance as a magnifying lens we demonstrate a feature broadening to a magnetic width of 8 G compared to a predicted Feshbach resonance width $\ll 0.1$~mG.

cond-mat.quant-gas↗

arXiv2021

Experimental observation of the avoided crossing of two $S$-matrix resonance poles in an ultracold atom collider

In quantum mechanics, collisions between two particles are captured by a scattering matrix which describes the transfer from an initial entrance state to an outgoing final state. Analyticity of the elements of this $S$-matrix enables their continuation onto the complex energy plane and opens up a powerful and widely used framework in scattering theory, where bound states and scattering resonances for a physical system are ascribed to $S$-matrix poles. In the Gedankenexperiment of gradually changing the potential parameters of the system, the complex energy poles will begin to move, and in their ensuing flow, two poles approaching will interact. An actual observation of this intriguing interaction between scattering poles in a collision experiment has, however, been elusive. Here, we expose the interplay between two scattering poles relating to a shape resonance and a magnetically tunable Feshbach resonance by studying ultracold atoms with a laser-based collider. We exploit the tunability of the Feshbach resonance to observe a compelling avoided crossing of the poles in their energies which is the hallmark of a strongly coupled system.

cond-mat.quant-gas↗

arXiv2019

Low-cost Wireless Condition Monitoring for an Ultracold Atom Machine

We present a flexible wireless monitoring system forbcondition-based maintenance and diagnostics tailored for dynamic and complex experimental setups encountered in modern research laboratories. Our platform leverages an Internet-of-Things approach to monitor a wide range of physical parameters via wireless sensor modules that broadcast to a networked computer. We give a specific demonstration for a so-called ultracold atom machine, which is the workhorse of many emerging quantum technologies and marries a broad spectrum of equipment and instrumentation into its setup. As a distinctive feature, our monitoring system taps into physical parameters of the ultracold atom machine both via customized sensor modules that directly perform measurements, and via modules that recruit and annex constituent instruments of the machine for the additional purpose of retrieving information for diagnostics.

physics.ins-det↗

arXiv2018

Deterministic quantum state transfer of atoms in a random magnetic field

We propose a method for transferring atoms to a target quantum state for a multilevel quantum system with sequentially increasing, but otherwise unknown, energy splitting. This is achieved with a feedback algorithm that processes off-resonant optical measurements of state populations during adiabatic rapid passage in real-time. Specifically, we reliably perform the transfer $|F=2,m_F=2\rangle \rightarrow |1,1\rangle \rightarrow |2,1\rangle$ for a sample of ultracold $^{87}$Rb in the presence of a random external magnetic field.

quant-ph↗

arXiv2018

Observation of bound state self-interaction in a nano-eV atom collider

Quantum mechanical scattering resonances for colliding particles occur when a continuum scattering state couples to a discrete bound state between them. The coupling also causes the bound state to interact with itself via the continuum and leads to a shift in the bound state energy, but, lacking knowledge of the bare bound state energy, measuring this self-energy via the resonance position has remained elusive. Here, we report on the direct observation of self-interaction by using a nano-eV atom collider to track the position of a magnetically-tunable Feshbach resonance through a parameter space spanned by energy and magnetic field. Our system of potassium and rubidium atoms displays a strongly non-monotonic resonance trajectory with an exceptionally large self-interaction energy arising from an interplay between the Feshbach bound state and a different, virtual bound state at a fixed energy near threshold.

cond-mat.quant-gas↗

arXiv2017

Quantum Scattering in an Optical Collider for Ultracold Atoms

We report on experiments investigating the collisional properties of atoms at ultralow collision energies using an all-optical atom collider. By using a pair of optical tweezers, we can manipulate two ultracold atom clouds and collide them together at energies up to three orders of magnitude larger than their thermal energy. Our experiments measure the scattering of $\rm ^{87}Rb$, $\rm ^{40}K$, and $\rm ^{40}K$-$\rm ^{87}Rb$ collisions. The versatility of our collider allows us to probe both shape resonances and Feshbach resonances in any partial wave. As examples, we present experiments demonstrating p-wave scattering with indistinguishable fermions, inelastic scattering at non-zero energies near a homonuclear Feshbach resonance, and partial wave interference in heteronuclear collisions.

cond-mat.quant-gas↗