Long-Lived Mesoscopic Entanglement outside the Lamb-Dicke Regime

McDonnell, Michael A.; Home, Jonathan; Lucas, David M.; Imreh, G.; Keitch, Ben; Szwer, D. J.; Thomas, Nathaniel R.; Webster, S. C.; Stacey, D. N.; Steane, Andrew M.

doi:10.1103/physrevlett.98.063603

Cited by 56 publications

(56 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…After three steps, each performed with a fidelity exceeding 0.99, we reveal the differences to a classical random walk. The limit of coherent displacements to states inside the Lamb-Dicke regime was foreseen by [14], experimentally observed in a different context [15], and is confirmed by us.In the experimental realization, we confine one 25 Mg + ion of mass m in a linear multi-zone Paul trap [16]. Motion in the axial (z -) direction is harmonic with an os-…”

supporting

confidence: 75%

supporting

confidence: 75%

“…More steps lead to higher motional excitations beyond the Lamb-Dicke regime where higher order effects in the interaction modify the transition rates. For our actual experimental realization, transition rates start to decrease around n = 8 (in our present implementation: n(1) = 1.33; n(2) = 4.71; n(3) = 9.08) leading to motional squeezing [15,22] and state reflection (Ω n,n+1 ≈ 0) at n ≈ 36 that cannot be overcome with the implemented walker steps. Reducing η by increasing the axial confinement and/or reducing the angle between the k-vectors of the Raman beams, and thus ∆k, should allow to extend this protocol to N ≤ 20 at comparable fidelities.…”

Section: Figmentioning

confidence: 90%

See 2 more Smart Citations

Quantum Walk of a Trapped Ion in Phase Space

Schmitz¹,

Matjeschk²,

Schneider³

et al. 2009

Phys. Rev. Lett.

465

448

View full text Add to dashboard Cite

We implement the proof of principle for the quantum walk of one ion in a linear ion trap. With a single-step fidelity exceeding 0.99, we perform three steps of an asymmetric walk on the line. We clearly reveal the differences to its classical counterpart if we allow the walker/ion to take all classical paths simultaneously. Quantum interferences enforce asymmetric, non-classical distributions in the highly entangled degrees of freedom (of coin and position states). We theoretically study and experimentally observe the limitation in the number of steps of our approach, that is imposed by motional squeezing. We propose an altered protocol based on methods of impulsive steps to overcome these restrictions, in principal allowing to scale the quantum walk to several hundreds of steps.PACS numbers: 03.67. Ac, 05.40Fb, 0504Jc A quantum walk[1] is the deterministic quantum mechanical extension of a classical random walk. A simple classical version requires two basic operations: Tossing the coin (coin-operation), allowing for two possible and random outcomes. Dependent on this outcome, the walker performs a step to the right or left (stepoperation). In the quantum mechanical extension the operations allow for coherent superpositions of entangled coin and position states. After several iterations the probability to be in a certain position is determined by quantum mechanical interference of the walker state that leads to fundamentally different characteristics of the walk [2].The motivation for studying quantum walks is twofold. On the one hand, many classical algorithms include random walks. Examples can be found in biology, psychology, economics and physics, for example Einstein's simple model for Brownian motion [3]. The extension of the walk to quantum mechanics might allow for substantial speedup of related quantum versions [2], as in prominent algorithms suggested by Shor[4] and Grover [5] due to other quantum-subroutines. On the other hand, the quantum walk could lead to new insights into entanglement and decoherence in mesoscopic systems [6]. These topics might be explored by increasing the amount of walkers -even before any algorithm might benefit from the quantum random walk.Quantum walks have been thoroughly investigated theoretically and first attempts at implementation have been performed with a very limited amount of steps due to a lack of operation fidelity or fundamental restrictions within the protocol. Some aspects have been realized on the longitudinal modes of a linear optical resonator [7] and in a nuclear magnetic resonance experiment [8]. An implementation based on neutral atoms in a spin-dependent optical lattice[9, 10, 11] has resulted in an experiment recently. Other proposals considered an array of microtraps illuminated by a set of microlenses [12] and Bose-Einstein condensates [13]. Travaglione and Milburn[14] proposed a scheme for trapped ions to transfer the high operational fidelities [6] obtained in quantum information processing (QIP) into To implement the deterministic "tossing of t...

show abstract

supporting

confidence: 75%

supporting

confidence: 75%

Section: Figmentioning

confidence: 90%

See 1 more Smart Citation

Quantum Walk of a Trapped Ion in Phase Space

Schmitz¹,

Matjeschk²,

Schneider³

et al. 2009

Phys. Rev. Lett.

465

448

View full text Add to dashboard Cite

show abstract

“…Therefore, we expect to observe quantum dynamics due to the strong-coupling effect. We note that the degenerate case has been investigated thoroughly for the production of Schrödinger's cat states [31][32][33][34][35][36] and the calibration of two-qubit Mølmer-Sørensen gates [37][38][39][40][41][42] in trapped-ion systems. Although the spin-dependent force is a welldeveloped technique for the trapped-ion community, it has never been viewed as the simulation of a special case of the QRM.…”

Section: Dsc Regime and Phonon Wave Packetsmentioning

confidence: 99%

Quantum Simulation of the Quantum Rabi Model in a Trapped Ion

et al. 2018

View full text Add to dashboard Cite

The quantum Rabi model, involving a two-level system and a bosonic field mode, is arguably the simplest and most fundamental model describing quantum light-matter interactions. Historically, due to the restricted parameter regimes of natural light-matter processes, the richness of this model has been elusive in the lab. Here, we experimentally realize a quantum simulation of the quantum Rabi model in a single trapped ion, where the coupling strength between the simulated light mode and atom can be tuned at will. The versatility of the demonstrated quantum simulator enables us to experimentally explore the quantum Rabi model in detail, including a wide range of otherwise unaccessible phenomena, as those happening in the ultrastrong and deep strong-coupling regimes. In this sense, we are able to adiabatically generate the ground state of the quantum Rabi model in the deep strong-coupling regime, where we are able to detect the nontrivial entanglement between the bosonic field mode and the two-level system. Moreover, we observe the breakdown of the rotating-wave approximation when the coupling strength is increased, and the generation of phonon wave packets that bounce back and forth when the coupling reaches the deep strongcoupling regime. Finally, we also measure the energy spectrum of the quantum Rabi model in the ultrastrong-coupling regime.

show abstract

“…In reference [77], for the condition described by Equation (6), the maximum separation of the wave packets was 4αz 0 83 nm, while the size of the wavepackets z 0 , was 7.1 nm (see also reference [78,79]). Of course, one might object to dignifying the state produced by calling it a Schrödinger cat since it is so small.…”

Section: Schrödinger's Catmentioning

confidence: 99%