arXiv subjects

J. G. E. Harris

Publications and source records attributed to J. G. E. Harris.

At least 19 recordsLinked to original sources

arXiv2026

Geometric Amplification via Non-Hermitian Berry Phase

Despite their apparent simplicity, coupled oscillators exhibit surprisingly complex phenomena. Two notable examples are Berry phase (a geometric or topological aspect of the oscillators' memory) and non-Hermiticity (the often counterintuitive impact of dissipation), both of which possess rich mathematical structures. Here, we demonstrate that combining Berry phase and non-Hermiticity leads to a fundamentally new form of amplification. Specifically, we show that this combination allows a lossy oscillator system to be converted into one with gain via slow modulation of its parameters. This is distinct from other amplification mechanisms, as it results specifically from the complex-valued Berry phase that is unique to non-Hermitian systems. We show that this mechanism produces continuous, useful gain in an optomechanical system, and that similar results can be realized in a very wide range of settings.

physics.class-ph↗

arXiv2024

A proposal for detecting the spin of a single electron in superfluid helium

The electron bubble in superfluid helium has two degrees of freedom that may offer exceptionally low dissipation: the electron's spin and the bubble's motion. If these degrees of freedom can be read out and controlled with sufficient sensitivity, they would provide a novel platform for realizing a range of quantum technologies and for exploring open questions in the physics of superfluid helium. Here we propose a practical scheme for accomplishing this by trapping an electron bubble inside a superfluid-filled opto-acoustic cavity.

quant-ph↗

arXiv2023

Quantum Sensors for High Energy Physics

Strong motivation for investing in quantum sensing arises from the need to investigate phenomena that are very weakly coupled to the matter and fields well described by the Standard Model. These can be related to the problems of dark matter, dark sectors not necessarily related to dark matter (for example sterile neutrinos), dark energy and gravity, fundamental constants, and problems with the Standard Model itself including the Strong CP problem in QCD. Resulting experimental needs typically involve the measurement of very low energy impulses or low power periodic signals that are normally buried under large backgrounds. This report documents the findings of the 2023 Quantum Sensors for High Energy Physics workshop which identified enabling quantum information science technologies that could be utilized in future particle physics experiments, targeting high energy physics science goals.

hep-ex↗

arXiv2023

Superfluid Helium Drops Levitated in High Vacuum

We demonstrate the trapping of millimeter-scale superfluid Helium drops in high vacuum. The drops are sufficiently isolated that they remain trapped indefinitely, cool by evaporation to 330 mK, and exhibit mechanical damping that is limited by internal processes. The drops are also shown to host optical whispering gallery modes. The approach described here combines the advantages of multiple techniques, and should offer access to new experimental regimes of cold chemistry, superfluid physics, and optomechanics.

cond-mat.other↗

arXiv2021

Nonclassical photon statistics in two-tone continuously driven optomechanics

In cavity optomechanics, single photon detection of Raman scattered photons can be a useful tool for observing nonclassical features of both radiation and motion. While this tool has been employed in experiments with pulsed laser driving of a cavity mode, it has not been readily accessible to experiments with continuous and constant laser driving. To address this, we present a study of a standard optomechanical system where the cavity mode is continuously driven at two different frequencies, and where sideband photons are detected by single photon detectors after frequency filtering the output from the cavity mode around its resonance frequency. We first derive the normalized second order coherence associated with the detected photons, and show that it contains signatures of the quantum nature of the mechanical mode which would be absent with only single-tone driving. To identify model-independent nonclassical features, we derive two inequalities for the sideband photon statistics that should be valid in any classical model of the system. We show that these inequalities are violated in the proposed setup. This is provided that the average phonon occupation number of the mechanical mode is sufficiently small, which in principle can be achieved through sideband cooling intrinsic to the setup. Violation of the first inequality means that there is no well-defined probability distribution of the Glauber-Sudarshan type for the cavity mode. In contrast, a violation of the second inequality means that there is no joint probability distribution for the cavity mode at two times separated by a finite interval, which originates from the noncommutativity of the motional quadratures of the mechanical mode. The proposed setup thus employs a mechanical oscillator in order to generate a steady-state source of nonclassical radiation.

quant-ph↗

arXiv2020

Non-Hermitian adiabatic transport in spaces of exceptional points

We consider the space of $n \times n$ non-Hermitian Hamiltonians ($n=2$, $3$, . . .) that are equivalent to a single $n\times n$ Jordan block. We focus on adiabatic transport around a closed path (i.e. a loop) within this space, in the limit as the time-scale $T=1/\varepsilon$ taken to traverse the loop tends to infinity. We show that, for a certain class of loops and a choice of initial state, the state returns to itself and acquires a complex phase that is $\varepsilon^{-1}$ times an expansion in powers of $\varepsilon^{1/n}$. The exponential of the term of $n$th order (which is equivalent to the "geometric" or Berry phase modulo $2π$), is thus independent of $\varepsilon$ as $\varepsilon\to0$; it depends only on the homotopy class of the loop and is an integer power of $e^{2πi/n}$. One of the conditions under which these results hold is that the state being transported is, for all points on the loop, that of slowest decay.

physics.class-ph↗

arXiv2020

Phase slip statistics of a single isolated flux-biased superconducting ring

We describe measurements of the thermally-activated transitions between fluxoid states of a single isolated superconducting ring. We compare these measurements with theoretical predictions in which all of the relevant parameters are determined via independent characterization of the same ring. This no-free-parameters comparison shows qualitative agreement over a wide range of temperatures. We discuss possible origins for the remaining discrepancies between the data and theory, in particular the choice of model for the superconducting order parameter's damping.

cond-mat.supr-con↗

arXiv2018

Nonreciprocal control and cooling of phonon modes in an optomechanical system

Phononic resonators play important roles in settings that range from gravitational wave detectors to cellular telephones. They serve as high-performance transducers, sensors, and filters by offering low dissipation, tunable coupling to diverse physical systems, and compatibility with a wide range of frequencies, materials, and fabrication processes. Systems of phononic resonators typically obey reciprocity, which ensures that the phonon transmission coefficient between any two resonators is independent of the direction of transmission. Reciprocity must be broken to realize devices (such as isolators and circulators) that provide one-way propagation of acoustic energy between resonators. Such devices are crucial for protecting active elements, mitigating noise, and operating full-duplex transceivers. To date, nonreciprocal phononic devices have not combined the features necessary for robust operation: strong nonreciprocity, in situ tunability, compact integration, and continuous operation. Furthermore, they have been applied only to coherent signals (rather than fluctuations or noise), and have been realized exclusively in travelling-wave systems (rather than resonators). Here we describe a cavity optomechanical scheme that produces robust nonreciprocal coupling between phononic resonators. This scheme provides ~ 30 dB of isolation and can be tuned in situ simply via the phases of the drive tones applied to the cavity. In addition, by directly monitoring the resonators' dynamics we show that this nonreciprocity can be used to control thermal fluctuations, and that this control represents a new resource for cooling phononic resonators.

physics.optics↗

arXiv2017

Quantum optomechanics in a liquid

Optomechanical systems provide a means for studying and controlling quantum effects in the motion of macroscopic objects. To date, quantum optomechanical effects have been studied in objects made from solids and gases. Here we describe measurements of quantum behavior in the vibrations of a liquid body. Specifically, we monitor the fluctuations of an individual acoustic standing wave in superfluid liquid helium, and find that it displays the characteristic signatures of zero-point motion and measurement back-action. This opens the possibility of exploiting the properties of liquids in general (and superfluid helium in particular) to access qualitatively new regimes of quantum optomechanics.

physics.optics↗

arXiv2017

Cavity Optomechanics in a Levitated Helium Drop

We describe a proposal for a new type of optomechanical system based on a drop of liquid helium that is magnetically levitated in vacuum. In the proposed device, the drop would serve three roles: its optical whispering gallery modes would provide the optical cavity, its surface vibrations would constitute the mechanical element, and evaporation of He atoms from its surface would provide continuous refrigeration. We analyze the feasibility of such a system in light of previous experimental demonstrations of its essential components: magnetic levitation of mm-scale and cm-scale drops of liquid He, evaporative cooling of He droplets in vacuum, and coupling to high-quality optical whispering gallery modes in a wide range of liquids. We find that the combination of these features could result in a device that approaches the single-photon strong coupling regime, due to the high optical quality factors attainable at low temperatures. Moreover, the system offers a unique opportunity to use optical techniques to study the motion of a superfluid that is freely levitating in vacuum (in the case of $^{4}\mathrm {He}$). Alternatively, for a normal fluid drop of $^3 \mathrm{He}$, we propose to exploit the coupling between the drop's rotations and vibrations to perform quantum non-demolition measurements of angular momentum.

quant-ph↗

arXiv2017

Topological dynamics in an optomechanical system with highly non-degenerate modes

Non-Hermitian systems exhibit phenomena that are qualitatively different from those of Hermitian systems and have been exploited to achieve a number of ends, including the generation of exceptional points, nonreciprocal dynamics, non-orthogonal normal modes, and topological operations. However to date these effects have only been accessible with nearly-degenerate modes (i.e., modes with frequency difference comparable to their linewidth and coupling rate). Here we demonstrate an optomechanical scheme that extends topological control to highly non-degenerate modes of a non-Hermitian system. Specifically, we induce a "virtual exceptional point" between two mechanical modes whose frequencies differ by >10^3 times their linewidth and coupling rate, and use adiabatic topological operations to transfer energy between these modes. This scheme can be readily implemented in many physical systems, potentially extending the utility of non-Hermitian dynamics to a much wider range of settings.

physics.optics↗

arXiv2016

Deterministic phase slips in mesoscopic superconducting rings

The properties of one-dimensional superconductors are strongly influenced by topological fluctuations of the order parameter, known as phase slips, which cause the decay of persistent current in superconducting rings and the appearance of resistance in superconducting wires. Despite extensive work, quantitative studies of phase slips have been limited by uncertainty regarding the order parameter's free energy landscape. Here we show detailed agreement between measurements of the persistent current in isolated flux-biased rings and Ginzburg-Landau theory over a wide range of temperature, magnetic field, and ring size; this agreement provides a quantitative picture of the free energy landscape. We also demonstrate that phase slips occur deterministically as the barrier separating two competing order parameter configurations vanishes. These results will enable studies of quantum and thermal phase slips in a well-characterized system and will provide access to outstanding questions regarding the nature of one-dimensional superconductivity.

cond-mat.supr-con↗

arXiv2016

Photothermal optomechanics in superfluid helium coupled to a fiber-based cavity

Presented in this paper are measurements of an optomechanical device in which various acoustic modes of a sample of superfluid helium couple to a fiber-based optical cavity. In contrast with recent work on the paraxial acoustic mode confined by the cavity mirrors, we focus specifically on the acoustic modes associated with the helium surrounding the cavity. This paper provides a framework for understanding how the acoustic modes depend on device geometry. The acoustic modes are observed using the technique of optomechanically induced transparency/amplification. The optomechanical coupling to these modes is found to be predominantly photothermal.

physics.optics↗

arXiv2016

Topological energy transfer in an optomechanical system with exceptional points

Topological operations have the merit of achieving certain goals without requiring accurate control over local operational details. To date, topological operations have been used to control geometric phases, and have been proposed as a means for controlling the state of certain systems within their degenerate subspaces[1-8]. More recently, it was predicted that topological operations can be extended to transfer energy between normal modes, provided that the system possesses a specific type of degeneracy known as an exceptional point (EP)[9-11]. Here we demonstrate the transfer of energy between two modes of a cryogenic optomechanical device by topological operations. We show that this transfer arises from the presence of an EP in the device's spectrum. We also show that this transfer is non-reciprocal[12-14]. These results open new directions in system control; they also open the possibility of exploring other dynamical effects related to EPs[15,16], as well as the behavior of thermal and quantum fluctuations in the vicinity of EPs.

physics.optics↗

arXiv2016

Superfluid Brillouin Optomechanics

Optomechanical systems couple an electromagnetic cavity to a mechanical resonator which is typically formed from a solid object. The range of phenomena accessible to these systems depends on the properties of the mechanical resonator and on the manner in which it couples to the cavity fields. In both respects, a mechanical resonator formed from superfluid liquid helium offers several appealing features: low electromagnetic absorption, high thermal conductivity, vanishing viscosity, well-understood mechanical loss, and in situ alignment with cryogenic cavities. In addition, it offers degrees of freedom that differ qualitatively from those of a solid. Here, we describe an optomechanical system consisting of a miniature optical cavity filled with superfluid helium. The cavity mirrors define optical and mechanical modes with near-perfect overlap, resulting in an optomechanical coupling rate ~3 kHz. This coupling is used to drive the superfluid; it is also used to observe the superfluid's thermal motion, resolving a mean phonon number as low as 11.

physics.optics↗

arXiv2015

Measurement of the motional sidebands of a nanogram-scale oscillator in the quantum regime

We describe measurements of the motional sidebands produced by a mechanical oscillator (with effective mass 43 ng and resonant frequency 705 kHz) that is placed in an optical cavity and cooled close to its quantum ground state. The red and blue sidebands (corresponding to Stokes and anti-Stokes scattering) from a single laser beam are recorded simultaneously via a heterodyne measurement. The oscillator's mean phonon number n is inferred from the ratio of the sidebands, and reaches a minimum value of 0.84 +- 0.22 (corresponding to a mode temperature T = 28 +- 7 microK). We also infer n from the calibrated area of each of the two sidebands, and from the oscillator's total damping. The values of n inferred from these four methods are in close agreement. The behavior of the sidebands as a function of the oscillator's temperature agrees well with theory that includes the quantum fluctuations of both the cavity field and the mechanical oscillator.

quant-ph↗

arXiv2014

Multimode optomechanical dynamics in a cavity with avoided crossings

Cavity optomechanics offers powerful methods for controlling optical fields and mechanical motion. A number of proposals have predicted that this control can be extended considerably in devices where multiple cavity modes couple to each other via the motion of a single mechanical oscillator. Here we study the dynamical properties of such a multimode optomechanical device, in which the coupling between cavity modes results from mechanically-induced avoided crossings in the cavity's spectrum. Near the avoided crossings we find that the optical spring shows distinct features that arise from the interaction between cavity modes. Precisely at an avoided crossing, we show that the particular form of the optical spring provides a classical analog of a quantum-nondemolition measurement of the intracavity photon number. The mechanical oscillator's Brownian motion, an important source of noise in these measurements, is minimized by operating the device at cryogenic temperature (500 mK).

quant-ph↗

arXiv2014

Fabrication and characterization of large arrays of mesoscopic gold rings on large-aspect-ratio cantilevers

We have fabricated large arrays of mesoscopic metal rings on ultrasensitive cantilevers. The arrays are defined by electron beam lithography and contain up to $10^5$ rings. The rings have a circumference of 1 $μ$m, and are made of ultrapure (6N) Au that is deposited onto a silicon-on-insulator wafer without an adhesion layer. Subsequent processing of the SOI wafer results in each array being supported at the end of a free-standing cantilever. To accommodate the large arrays while maintaining a low spring constant, the cantilevers are nearly 1 mm in both lateral dimensions and 100 nm thick. The extreme aspect ratio of the cantilevers, the large array size, and the absence of a sticking layer are intended to enable measurements of the rings' average persistent current $\langle I \rangle$ in the presence of relatively small magnetic fields. We describe the motivation for these measurements, the fabrication of the devices, and the characterization of the cantilevers' mechanical properties. We also discuss the devices' expected performance in measurements of $\langle I \rangle$.

cond-mat.mes-hall↗