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A. Ruschhaupt

Publications and source records attributed to A. Ruschhaupt.

At least 19 recordsLinked to original sources
arXiv2025

Improved anharmonic trap expansion through enhanced shortcuts to adiabaticity

Shortcuts to adiabaticity (STA) have been successfully applied both theoretically and experimentally to a wide variety of quantum control tasks. In previous work the authors have developed an analytic extension to shortcuts to adiabaticity, called enhanced shortcuts to adiabaticity (eSTA), that extends STA methods to systems where STA cannot be applied directly [Phys. Rev. Research 2, 023360 (2020)]. Here we generalize this approach and construct an alternative eSTA method that takes advantage of higher order terms. We apply this eSTA method to the expansion of both a Gaussian trap and accordion lattice potential, demonstrating the improved fidelity and robustness of eSTA.

quant-ph↗
arXiv2019

Shortcuts to adiabaticity: concepts, methods, and applications

Shortcuts to adiabaticity (STA) are fast routes to the final results of slow, adiabatic changes of the controlling parameters of a system. The shortcuts are designed by a set of analytical and numerical methods suitable for different systems and conditions. A motivation to apply STA methods to quantum systems is to manipulate them on timescales shorter than decoherence times. Thus shortcuts to adiabaticity have become instrumental in preparing and driving internal and motional states in atomic, molecular, and solid-state physics. Applications range from information transfer and processing based on gates or analog paradigms to interferometry and metrology. The multiplicity of STA paths for the controlling parameters may be used to enhance robustness versus noise and perturbations or to optimize relevant variables. Since adiabaticity is a widespread phenomenon, STA methods also extended beyond the quantum world to optical devices, classical mechanical systems, and statistical physics. Shortcuts to adiabaticity combine well with other concepts and techniques, in particular, with optimal control theory, and pose fundamental scientific and engineering questions such as finding speed limits, quantifying the third law, or determining process energy costs and efficiencies. Concepts, methods, and applications of shortcuts to adiabaticity are reviewed and promising prospects are outlined, as well as open questions and challenges ahead.

quant-ph↗
arXiv2018

Selective population of a large-angular-momentum state in an optical lattice

We propose a method to selectively populate a large angular momentum state of ultracold atoms (each with an orbital angular momentum $l \approx 2 \hbar$) in the Mott regime of a two-dimensional optical lattice. This is done by periodically modulating the lattice amplitude and implementing an additional rectangular lattice of shorter wavelength at an angle of $π/4$. The specific pulse sequences are designed using a four-level model for each well and are implemented sequentially. The results are confirmed with numerical simulations of the full Schroedinger equation. The methods of this paper are another step in constructing a modular toolbox of operations for creating higher orbital states in optical lattices.

quant-ph↗
arXiv2018

Fast shuttling of a particle under weak spring-constant noise of the moving trap

We investigate the excitation of a quantum particle shuttled in a harmonic trap with weak springconstant colored noise. The Ornstein-Uhlenbeck model for the noise correlation function describes a wide range of possible noises, in particular for short correlation times the white-noise limit examined in Lu et al, Phys. Rev. A 89, 063414 (2014) and, by averaging over correlation times, "1/f ficker noise". We find expressions for the excitation energy in terms of static (independent of trap motion) and dynamical sensitivities, with opposite behavior with respect to shuttling time, and demonstrate that the excitation can be reduced by proper process timing and design of the trap trajectory.

quant-ph↗
arXiv2017

Asymmetric scattering by non-hermitian potentials

The scattering of quantum particles by non-hermitian (generally nonlocal) potentials in one dimension may result in asymmetric transmission and/or reflection from left and right incidence. Eight generalized symmetries based on the discrete Klein's four-group (formed by parity, time reversal, their product, and unity) are used together with generalized unitarity relations to determine the possible and/or forbidden scattering asymmetries. Six basic device types are identified when the scattering coefficients (squared moduli of scattering amplitudes) adopt zero/one values, and transmission and/or reflection are asymmetric. They can pictorially be described as a one-way mirror, a one-way barrier (a Maxwell pressure demon), one-way (transmission or reflection) filters, a mirror with unidirectional transmission, and a transparent, one-way reflector. We design potentials for these devices and also demonstrate that the behavior of the scattering coefficients can be extended to a broad range of incident momenta.

quant-ph↗
arXiv2017

Energy consumption for Shortcuts To Adiabaticity

Shortcuts to adiabaticity let a system reach the results of a slow adiabatic process in a shorter time. We propose to quantify the "energy cost" of the shortcut by the energy consumption of the system enlarged by including the control device. A mechanical model where the dynamics of the system and control device can be explicitly described illustrates that a broad range of possible values for the consumption are possible, including zero (above the adiabatic energy increment) when friction is negligible and the energy given away as negative power is stored and recovered by perfect regenerative braking.

quant-ph↗
arXiv2017

Local rectification of heat flux

We present a chain-of-atoms model where heat is rectified, with different fluxes from the hot to the cold baths located at the chain boundaries when the temperature bias is reversed. The chain is homogeneous except for boundary effects and a local modification of the interactions at one site, the "impurity". The rectification mechanism is due here to the localized impurity, the only asymmetrical element of the structure, apart from the externally imposed temperature bias, and does not rely on putting in contact different materials or other known mechanisms such as grading or long-range interactions. The effect survives if all interaction forces are linear except the ones for the impurity.

cond-mat.stat-mech↗
arXiv2016

Fast separation of two trapped ions

We design fast protocols to separate or recombine two ions in a segmented Paul trap. By inverse engineering the time evolution of the trapping potential composed of a harmonic and a quartic term, it is possible to perform these processes in a few microseconds without final excitation. These times are much shorter than the ones reported so far experimentally. The design is based on dynamical invariants and dynamical normal modes. Anharmonicities beyond the harmonic approximation at potential minima are taken into account perturbatively. The stability versus an unknown potential bias is also studied.

quant-ph↗
arXiv2015

Shortcuts to adiabaticity

Quantum adiabatic processes -that keep constant the populations in the instantaneous eigenbasis of a time-dependent Hamiltonian- are very useful to prepare and manipulate states, but take typically a long time. This is often problematic because decoherence and noise may spoil the desired final state, or because some applications require many repetitions. "Shortcuts to adiabaticity" are alternative fast processes which reproduce the same final populations, or even the same final state, as the adiabatic process in a finite, shorter time. Since adiabatic processes are ubiquitous, the shortcuts span a broad range of applications in atomic, molecular and optical physics, such as fast transport of ions or neutral atoms, internal population control and state preparation (for nuclear magnetic resonance or quantum information), cold atom expansions and other manipulations, cooling cycles, wavepacket splitting, and many-body state engineering or correlations microscopy. Shortcuts are also relevant to clarify fundamental questions such as a precise quantification of the third principle of thermodynamics and quantum speed limits. We review different theoretical techniques proposed to engineer the shortcuts, the experimental results, and the prospects.

quant-ph↗
arXiv2015

Fast quasi-adiabatic dynamics

We work out the theory and applications of a fast quasi-adiabatic approach to speed up slow adiabatic manipulations of quantum systems by driving a control parameter as near to the adiabatic limit as possible over the entire protocol duration. Specifically, we show that the population inversion in a two-level system, the splitting and cotunneling of two-interacting bosons, and the stirring of a Tonks-Girardeau gas on a ring to achieve mesoscopic superpositions of many-body rotating and non-rotating states, can be significantly speeded up.

quant-ph↗
arXiv2014

Fast and stable manipulation of a charged particle in a Penning trap

We propose shortcuts to adiabaticity which achieve fast and stable control of the state of a charged particle in an electromagnetic field. In particular we design a non-adiabatic change of the magnetic field strength in a Penning trap which changes the radial spread without final excitations. We apply a streamlined version of the fast-forward formalism as well as an invariant based inverse engineering approach. We compare both methods and examine their stability.

quant-ph↗
arXiv2014

Fast shuttling of a trapped ion in the presence of noise

We theoretically investigate the motional excitation of a single ion caused by spring-constant and position uctuations of a harmonic trap during trap shuttling processes. A detailed study of the sensitivity on noise for several transport protocols and noise spectra is provided. The effect of slow spring-constant drifts is also analyzed. Trap trajectories that minimize the excitation are designed combining invariant-based inverse engineering, perturbation theory, and optimal control.

quant-ph↗
arXiv2013

Fast and robust population transfer in two-level quantum systems with dephasing noise and/or systematic frequency errors

We design, by invariant-based inverse engineering, driving fields that invert the population of a two-level atom in a given time, robustly with respect to dephasing noise and/or systematic frequency shifts. Without imposing constraints, optimal protocols are insensitive to the perturbations but need an infinite energy. For a constrained value of the Rabi frequency, a flat $π$ pulse is the least sensitive protocol to phase noise but not to systematic frequency shifts, for which we describe and optimize a family of protocols.

quant-ph↗
arXiv2013

Robust quantum control by shaped pulse

Considering the problem of the control of a two-state quantum system by an external field, we establish a general and versatile method that allows the derivation of smooth pulses, suitable for ultrafast applications, that feature the properties of high-fidelity, robustness, and low area. Such shaped pulses can be viewed as a single-shot generalization of the composite pulse technique with a time-dependent phase.

quant-ph↗
arXiv2012

Optimizing the catching of atoms or molecules in two-dimensional traps

Single-photon cooling is a recently introduced method to cool atoms and molecules for which standard methods might not be applicable. We numerically examine this method in a two-dimensional wedge trap as well as in a two-dimensional harmonic trap. An element of the method is an optical dipole box trapping atoms irreversibly. We show that the cooling efficiency of the single-photon method can be improved by optimizing the trajectory of this optical dipole box.

quant-ph↗
arXiv2012

Optimally robust shortcuts to population inversion in two-level quantum systems

We examine the stability versus different types of perturbations of recently proposed shortcuts-to-adiabaticity to speed up the population inversion of a two-level quantum system. We find optimally robust processes using invariant based engineering of the Hamiltonian. Amplitude noise and systematic errors require different optimal protocols.

quant-ph↗
arXiv2012

Shortcuts to adiabaticity: fast-forward approach

The "fast-forward" approach by Masuda and Nakamura generates driving potentials to accelerate slow quantum adiabatic dynamics. First we present a streamlined version of the formalism that produces the main results in a few steps. Then we show the connection between this approach and inverse engineering based on Lewis-Riesenfeld invariants. We identify in this manner applications in which the engineered potential does not depend on the initial state. Finally we discuss more general applications exemplified by wave splitting processes.

quant-ph↗