arXiv subjects

Ravid Shaniv

Publications and source records attributed to Ravid Shaniv.

14 recordsLinked to original sources

arXiv2026

Extending the fundamental limit of atomic clock stability

Optical atomic clocks have been rapidly developing in recent decades, resulting in major improvements in both precision and accuracy. As a result, they have become instrumental in multiple areas of applied and fundamental research. Despite all atomic frequency references having more than two energy-levels, the commonly used model for evaluating their ultimate limits assumes a two-level atom. This leads to frequency interrogation protocols and theoretical stability bounds that are suboptimal for a true multi-level atom. The most fundamental stability bound assumes two noise sources - quantum projection noise and spontaneous decay from the excited state. In this work, we analyze a model that includes these noise types and is generalized beyond the two-level assumption, where spontaneous decay can branch to more than a single ground state. This model allows for detection and exclusion of atomic frequency interrogations in which the atom decayed, leading to a frequency stability improvement of up to $\approx 4.5 \text{ dB}$ compared with the two-level model. Furthermore, we identify an even greater stability enhancement of $\approx 5.4 \text{ dB}$ for frequency comparisons between atoms in an odd parity Bell state. These enhancements are particularly relevant for the numerous trapped-ion optical clock species that operate close to lifetime-limited stability. We calculate new stability limits for those cases and provide a detailed experimental protocol for frequency interrogation with an $^{27}\text{Al}^{+}$ optical ion clock.

physics.atom-ph↗

arXiv2025

High Stability Mechanical Frequency Sensing beyond the Linear Regime

Sensing via a mechanical frequency shift is a powerful measurement tool, and, therefore, understanding and mitigating frequency noise affecting mechanical resonators is imperative. Thermomechanical noise fundamentally limits mechanical frequency stability, and its impact can be reduced with increased coherent amplitude of mechanical motion. However, large enough actuation places the resonator in the nonlinear (Duffing) regime, where conversion of amplitude noise (AM) into frequency noise (FM) can worsen sensor performance. Here, we present an experimentally straightforward method to evade this amplitude tradeoff in micromechanical sensors. Combining knowledge of the Duffing coefficients with readily available amplitude measurements, we avoid AM-FM conversion. Our approach uses dual-mechanical-mode operation on a tensioned thin-film resonator to set a baseline thermomechanically-limited stability by eliminating correlated single-mode frequency drifts. Thus, we cleanly observe AM-FM conversion at high drive, and reduce it using our method. The resulting high-stability operation beyond the linear regime contrasts long-standing perspectives in the field.

cond-mat.mes-hall↗

arXiv2023

Direct Measurement of A Spatially Varying Thermal Bath Using Brownian Motion

Micro-mechanical resonator performance is fundamentally limited by the coupling to a thermal environment. The magnitude of this thermodynamical effect is typically considered in accordance with a physical temperature, assumed to be uniform across the resonator's physical span. However, in some circumstances, e.g. quantum optomechanics or interferometric gravitational wave detection, the temperature of the resonator may not be uniform, resulting in the resonator being thermally linked to a spatially varying thermal bath. In this case, the link of a mode of interest to its thermal environment is less straightforward to understand. Here, we engineer a distributed bath on a germane optomechanical platform -- a phononic crystal -- and utilize both highly localized and extended resonator modes to probe the spatially varying bath in entirely different bath regimes. As a result, we observe striking differences in the modes' Brownian motion magnitude. From these measurements we are able to reconstruct the local temperature map across our resonator and measure nanoscale effects on thermal conductivity and radiative cooling. Our work explains some thermal phenomena encountered in optomechanical experiments, e.g. mode-dependent heating due to light absorption. Moreover, our work generalizes the typical figure of merit quantifying the coupling of a resonator mode to its thermal environment from the mechanical dissipation to the overlap between the local dissipation and the local temperature throughout the resonator. This added understanding identifies design principles that can be applied to performance of micro-mechanical resonators.

cond-mat.mes-hall↗

arXiv2022

Understanding the Quality Factor of Mass-Loaded Tensioned Resonators

Mechanical resonators featuring large tensile stress have enabled a range of experiments in quantum optomechanics and novel sensing. Many sensing applications require functionalizing tensioned resonators by appending additional mass to them. However, this may dramatically change the resonator mode quality factor, and hence its sensitivity. In this work, we investigate the effect of the crossover from no mass load to a large mass load on the mode shape and quality factor of a tensioned resonator. We show through an analytical model and finite element analysis that as the load mass increases, surprisingly, the resonator mode shape becomes independent of the exact load mass, and therefore, its quality factor saturates. We validate this saturation effect experimentally by measuring the quality factor of a silicon nitride trampoline resonator while varying the load mass in a controlled manner.

cond-mat.mes-hall↗

arXiv2019

Theory of robust multi-qubit non-adiabatic gates for trapped-ions

The prevalent approach to executing quantum algorithms on quantum computers is to break-down the algorithms to a concatenation of universal gates, typically single and two-qubit gates. However such a decomposition results in long gate sequences which are exponential in the qubit register size. Furthermore, gate fidelities tend to decrease when acting in larger qubit registers. Thus high-fidelity implementations in large qubit registers is still a prominent challenge. Here we propose and investigate multi-qubit entangling gates for trapped-ions. Our gates couple many qubits at once, allowing to decrease the total number of gates used while retaining a high gate fidelity. Our method employs all of the normal-modes of motion of the ion chain, which allows to operate outside of the adiabatic regime and at rates comparable to the secular ion-trapping frequency. Furthermore we extend our method for generating Hamiltonians which are suitable for quantum analog simulations, such as a nearest-neighbour spin Hamiltonian or the Su-Schrieffer-Heeger Hamiltonian.

quant-ph↗

arXiv2019

Precision measurement of atomic isotope shifts using a two-isotope entangled state

Atomic isotope shifts (ISs) are the isotope-dependent energy differences in the atomic electron energy levels. These shifts serve an important role in atomic and nuclear physics, and particularly in the latter as signatures of nuclear structure. Recently ISs have been suggested as unique probes of beyond Standard Model (SM) physics, under the condition that they be determined significantly more precisely than current state of the art. In this work we present a simple and robust method for measuring ISs with ions in a Paul trap, by taking advantage of Hilbert subspaces that are insensitive to common-mode noise yet sensitive to the IS. Using this method we evaluate the IS of the $5S_{1/2}\leftrightarrow4D_{5/2}$ transition in $^{86}\text{Sr}^+$ and $^{88}\text{Sr}^+$ with a $1.6\times10^{-11}$ relative uncertainty to be 570,264,063.435(9) Hz. Furthermore, we detect a relative difference of $3.46(23)\times10^{-8}$ between the orbital g-factors of the electrons in the $4D_{5/2}$ level of the two isotopes. Our method is relatively easy to implement and is indifferent to element or isotope, paving the way for future tabletop searches for new physics and posing interesting prospects for testing quantum many-body calculations and for the study of nuclear structure.

physics.atom-ph↗

arXiv2019

Constraining Rapidly Oscillating Scalar Dark Matter Using Dynamic Decoupling

We propose and experimentally demonstrate a method for detection of light scalar Dark Matter (DM), through probing temporal oscillations of fundamental constants in an atomic optical transition. Utilizing the quantum information notion of Dynamic Decoupling (DD) in a table-top setting, we are able to obtain model-independent bounds on variations of $α$ and $m_e$ at frequencies up to the MHz scale. We interpret our results to constrain the parameter space of light scalar DM field models. We consider the generic case, where the couplings of the DM field to the photon and to the electron are independent, as well as the case of a relaxion DM model, including the scenario of a DM boson star centered around Earth. Given the particular nature of DD, allowing to directly observe the oscillatory behaviour of coherent DM, and considering future experimental improvements, we conclude that our proposed method could be complimentary to, and possibly competitive with, gravitational probes of light scalar DM.

hep-ph↗

arXiv2018

Quadrupole shift cancellation using dynamic decoupling

We present a method that uses radio-frequency pulses to cancel the quadrupole shift in optical clock transitions. Quadrupole shifts are an inherent inhomogeneous broadening mechanism in trapped ion crystals, limiting current optical ion clocks to work with a single probe ion. Cancelling this shift at each interrogation cycle of the ion frequency allows the use of $N>1$ ions in clocks, thus reducing the uncertainty in the clock frequency by $\sqrt{N}$ according to the standard quantum limit. Our sequence relies on the tensorial nature of the quadrupole shift, and thus also cancels other tensorial shifts, such as the tensor ac stark shift. We experimentally demonstrate our sequence on three and seven $^{88}\mathrm{Sr}^{+}$ ions trapped in a linear Paul trap, using correlation spectroscopy. We show a reduction of the quadrupole shift difference between ions to $\approx20$ mHz's level where other shifts, such as the relativistic 2$^{\mathrm{nd}}$ order Doppler shift, are expected to limit our spectral resolution. In addition, we show that using radio-frequency dynamic decoupling we can also cancel the effect of 1$^{\mathrm{st}}$ order Zeeman shifts.

quant-ph↗

arXiv2018

Robust entanglement gates for trapped-ion qubits

High-fidelity two-qubit entangling gates play an important role in many quantum information processing tasks and are a necessary building block for constructing a universal quantum computer. Such high-fidelity gates have been demonstrated on trapped-ion qubits, however, control errors and noise in gate parameters may still lead to reduced fidelity. Here we propose and demonstrate a general family of two-qubit entangling gates which are robust to different sources of noise and control errors. These gates generalize the celebrated Mølmer-Sørensen gate by using multi-tone drives. We experimentally implemented several of the proposed gates on $^{88}\text{Sr}^{+}$ ions trapped in a linear Paul trap, and verified their resilience.

quant-ph↗

arXiv2017

New ideas for tests of Lorentz invariance with atomic systems

We describe a broadly applicable experimental proposal to search for the violation of local Lorentz invariance (LLI) with atomic systems. The new scheme uses dynamic decoupling and can be implemented in current atomic clocks experiments, both with single ions and arrays of neutral atoms. Moreover, the scheme can be performed on systems with no optical transitions, and therefore it is also applicable to highly charged ions which exhibit particularly high sensitivity to Lorentz invariance violation. We show the results of an experiment measuring the expected signal of this proposal using a two-ion crystal of $^{88}$Sr$^+$ ions. We also carry out a systematic study of the sensitivity of highly charged ions to LLI to identify the best candidates for the LLI tests.

quant-ph↗

arXiv2017

Heisenberg-limited Rabi spectroscopy

The use of entangled states was shown to improve the fundamental limits of spectroscopy to beyond the standard-quantum limit. In these Heisenberg-limited protocols the phase between two states in an entangled superposition evolves N-fold faster than in the uncorrelated case, where N for example can be the number of entangled atoms in a Greenberger-Horne-Zeilinger (GHZ) state. Here we propose and demonstrate the use of correlated spin-Hamiltonians for the realization of Heisenberg-limited Rabi-type spectroscopy. Rather than probing the free evolution of the phase of an entangled state with respect to a local oscillator (LO), we probe the evolution of an, initially separable, two-atom register under an Ising spin-Hamiltonian with a transverse field. The resulting correlated spin-rotation spectrum is twice as narrow as compared with uncorrelated rotation. We implement this Heisenberg-limited Rabi spectroscopy scheme on the optical-clock electric-quadrupole transition of $^{88}$Sr$^+$ using a two-ion crystal. We further show that depending on the initial state, correlated rotation can occur in two orthogonal sub-spaces of the full Hilbert space, yielding Heisenberg-limited spectroscopy of either the average transition frequency of the two ions or their difference from the mean frequency. The potential improvement of clock stability due to the use of entangled states depends on the details of the method used and the dominating decoherence mechanism. The use of correlated spin-rotations can therefore potentially lead to new paths for clock stability improvement.

quant-ph↗

arXiv2017

Fast dynamical decoupling of the Molmer-Sorensen entangling gate

Engineering entanglement between quantum systems often involves coupling through a bosonic mediator, which should be disentangled from the systems at the operation's end. The quality of such an operation is generally limited by environmental and control noise. One of the prime techniques for suppressing noise is by dynamical decoupling, where one actively applies pulses at a rate that is faster than the typical time scale of the noise. However, for boson-mediated gates, current dynamical decoupling schemes require executing the pulses only when the boson and the quantum systems are disentangled. This restriction implies an increase of the gate time by a factor of $\sqrt{N}$, with $N$ being the number of pulses applied. Here we propose and realize a method that enables dynamical decoupling in a boson mediated system where the pulses can be applied while spin-boson entanglement persists, resulting in an increase in time that is at most a factor of $\fracπ{2}$, independently of the number of pulses applied. We experimentally demonstrate the robustness of our fast dynamically decoupled entangling gate to $σ_z$ noise with ions in a Paul trap.

physics.atom-ph↗

arXiv2016

Quantum Lock-in Force Sensing using Optical Clock Doppler Velocimetry

Force sensors are at the heart of different technologies such as atomic force microscopy or inertial sensing \cite{RMPforce2003, Rugar2004, YazdiIEEE}. These sensors often rely on the measurement of the displacement amplitude of mechanical oscillators under applied force. Examples for such mechanical oscillators include micro-fabricated cantilevers \cite{YazdiIEEE}, carbon nanotubes \cite{NanotubeForce} as well as single trapped ions \cite{Bollinger, Udem} . The best sensitivity is typically achieved when the force is alternating at the mechanical resonance frequency of the oscillator thus increasing its response by the mechanical quality factor. The measurement of low-frequency forces, that are below resonance, is a more difficult task as the resulting oscillation amplitudes are significantly lower. Here we use a single trapped $^{88}Sr^{+}$ ion as a force sensor. The ion is trapped in a linear harmonic trap, and is electrically driven at a frequency much lower than the trap resonance frequency. To be able to measure the small amplitude of motion we combine two powerful techniques. The force magnitude is determined by the measured periodic Doppler shift of an atomic optical clock transition and the Quantum Lock-in technique is used to coherently accumulate the phases acquired during different force half-cycles. We demonstrate force detection both when the oscillating force is phase-synchronized with the quantum lock-in sequence and when it is asynchronous and report frequency force detection sensitivity as low as $5.3\times10^{-19}\frac{\mathrm{N}}{\sqrt{\mathrm{Hz}}}$ .

quant-ph↗

arXiv2015

Atomic Quadrupole Moment Measurement Using Dynamic Decoupling

We present a method that uses dynamic decoupling of a multi-level quantum probe to distinguish small frequency shifts that depend on $m^2_{j}$, where $m^2_{j}$ is the angular momentum of level $\left|j\right\rangle$ along the quantization axis, from large noisy shifts that are linear in $m_{j}$, such as those due to magnetic field noise. Using this method we measured the electric quadrupole moment of the $4D_{\frac{5}{2}}$ level in $^{88}Sr^{+}$ to be $2.973^{+0.026}_{-0.033}\, ea_{0}^{2}$. Our measurement improves the uncertainty of this value by an order of magnitude and thus helps mitigate an important systematic uncertainty in $^{88}Sr^{+}$ based optical atomic clocks and verifies complicated many-body quantum calculations.

quant-ph↗