Creation of entangled states of distant atoms by interference

Cabrillo, C.; Cirac, J. I.; Garcı́a-Fernández, P.; Zoller, P.

doi:10.1103/physreva.59.1025

Cited by 560 publications

(589 citation statements)

References 24 publications

Supporting

Mentioning

549

Contrasting

Order By: Relevance

“…These phase-locked photons are ideally suited for quantum interference applications, which form the basis of quantum communication 18 , linear optics quantum computation 35 and distant entanglement schemes 10,11 . The price to pay for this unprecedented photon quality is excitation efficiency.…”

Section: Discussionmentioning

confidence: 99%

“…Further, non-unity photon collection and detector efficiencies evidently render any measurement-based schemes probabilistic. Second, an entanglement rate scaling with the two-photon detection efficiency 11 is replaced advantageously by one-photon detection 10,18 , utilizing the first-order coherence of the coherently scattered photons. The technique presented in the work is not limited to QDs and can be extended to other quantum systems in the optical domain as well as to superconducting circuits in the microwave domain.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Phase-locked indistinguishable photons with synthesized waveforms from a solid-state source

et al. 2013

View full text Add to dashboard Cite

Resonance fluorescence in the Heitler regime provides access to single photons with coherence well beyond the Fourier transform limit of the transition, and holds the promise to circumvent environment-induced dephasing common to all solid-state systems. Here we demonstrate that the coherently generated single photons from a single self-assembled InAs quantum dot display mutual coherence with the excitation laser on a timescale exceeding 3 s. Exploiting this degree of mutual coherence, we synthesize near-arbitrary coherent photon waveforms by shaping the excitation laser field. In contrast to post-emission filtering, our technique avoids both photon loss and degradation of the single-photon nature for all synthesized waveforms. By engineering pulsed waveforms of single photons, we further demonstrate that separate photons generated coherently by the same laser field are fundamentally indistinguishable, lending themselves to the creation of distant entanglement through quantum interference.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Phase-locked indistinguishable photons with synthesized waveforms from a solid-state source

et al. 2013

View full text Add to dashboard Cite

show abstract

“…47,48 For hyperfine atomic qubits, the optical path length of this interferometer need only be stabilised to well within the wavelength corresponding to the qubit frequency difference (~mm). The mean connection rate of this photonic interface is R Fη D ð Þ 2 =2, where F is the fraction of light collection from each ion emitter, η D is the single-photon detector efficiency and R is the repetition rate of the initialisation/excitation process limited by the emission rate γ (an alternative singlephoton approach involving the weak excitation of the ions 49,50 suffers from optical path length instabilities, and, as the light collection improves, the performance of this alternative protocol is inferior to the two-photon scheme discussed in the text.). For typical atomic transitions into free space with γ/2π~10 MHz, light collection fraction F~1-10% and detector efficiency η D~2 0%, we find typical connection rates of~100 Hz, 51 but this could be markedly improved with integrated photonics, as discussed below.…”

Section: Ion Trap Qubits and Wiresmentioning

confidence: 99%

Co-designing a scalable quantum computer with trapped atomic ions

2016

View full text Add to dashboard Cite

The first generation of quantum computers are on the horizon, fabricated from quantum hardware platforms that may soon be able to tackle certain tasks that cannot be performed or modelled with conventional computers. These quantum devices will not likely be universal or fully programmable, but special-purpose processors whose hardware will be tightly co-designed with particular target applications. Trapped atomic ions are a leading platform for first-generation quantum computers, but they are also fundamentally scalable to more powerful general purpose devices in future generations. This is because trapped ion qubits are atomic clock standards that can be made identical to a part in 10 15 , and their quantum circuit connectivity can be reconfigured through the use of external fields, without modifying the arrangement or architecture of the qubits themselves. In this forwardlooking overview, we show how a modular quantum computer with thousands or more qubits can be engineered from ion crystals, and how the linkage between ion trap qubits might be tailored to a variety of applications and quantum-computing protocols. Quantum information processors have the potential to perform computational tasks that are difficult or impossible using conventional modes of computing. 1-3 In a radical departure from classical information, the qubits of a quantum computer can simultaneously store bit values 0 and 1, and when measured they probabilistically assume definite states. Many interacting qubits, isolated from their environment, can represent huge amounts of information: there are exponentially many binary numbers that can co-exist, with entangled qubit correlations that can behave as invisible wires between the qubits. Even in the face of Moore's Law, or the doubling in conventional computer power every year or two, the complexity of massively entangled quantum states of just a few hundred qubits can easily eclipse the capacity of classical information processing. 4 There are but a few known applications that exploit this quantum advantage, such as Shor's factoring algorithm, 5 and future quantum information processors will likely be applied to special-purpose applications. On the other hand, a quantum computer has not yet been built; therefore, new quantum applications and algorithms will likely follow from the evolution and capability of quantum hardware.In the 20 years since the advent of Shor's algorithm 5 and the discovery of quantum error correction, 6-8 there has been remarkable progress in demonstrations of entangling quantum gates on o10 qubits in certain physical systems. Current efforts aim to scale to hundreds, thousands or even millions of interacting qubits. Unlike the classical scaling of bits and logic gates, however, large quantum systems are not comparable to the behaviour of just a few qubits. Just because 2 or 4 qubits can be completely controlled with negligible errors does not mean that this system can readily scale to 4100 qubits.In the last few years, two particular quantum hardware platforms have e...

show abstract

“…al. [8] proposes preparing two spatially separated atoms in their long-lived excited states |1 A |1 B . A single-photon detector that cannot even in principle distinguish the direction from which a detected photon arrives is placed half way between the atoms.…”

Section: Some Promising Directions For Future Researchmentioning

confidence: 99%

Lorentz-invariant look at quantum clock-synchronization protocols based on distributed entanglement

Yurtsever

Dowling

2002

Phys. Rev. A

View full text Add to dashboard Cite

Recent work has raised the possibility that quantum information theory techniques can be used to synchronize atomic clocks nonlocally. One of the proposed algorithms for quantum clock synchronization (QCS) requires distribution of entangled pure singlets to the synchronizing parties. Such remote entanglement distribution normally creates a relative phase error in the distributed singlet state which then needs to be purified asynchronously. We present a fully relativistic analysis of the QCS protocol which shows that asynchronous entanglement purification is not possible, and, therefore, that the proposed QCS scheme remains incomplete. We discuss possible directions of research in quantum information theory which may lead to a complete, working QCS protocol. Clock synchronization with shared singletsSuppose a supply of identical but distinguishable twostate systems (e.g. atoms) are available whose betweenstate transitions can be manipulated (e.g. by laser pulses). Let |1 and |0 denote, respectively, the excited and ground states (which span the internal Hilbert space H) of the prototype two-state system, and let the energy difference between the two states be Ω (we will use units in which = c = 1 throughout this letter). Without loss of generality, we can assumewhere H 0 denotes the internal Hamiltonian. Suppose pairs of these two-state systems are distributed to two spatially-separated observers Alice and Bob. The Hilbert space of each pair can be written as H A ⊗ H B , where ⊗ denotes tensor product between vector spaces. A ("pure") singlet is the specific entangled quantum state in this product Hilbert space given by[in what follows, we will omit tensor-product signs in expressions of the kind Eq. (2) unless required for clarity]. Two important properties of the singlet state Ψ are: (i) it is a "dark" state (invariant up to a multiplicative phase factor) under the time evolution U t ≡ exp(itH 0 ), i.e. (U t ⊗ U t )Ψ = e iφ Ψ where e iφ is an overall phase, and (ii) it is similarly invariant under all unitary transformations of the form U ⊗ U , where U is any arbitrary unitary map on H (not necessarily equal to U t ). Both properties are needed for the Quantum Clock Synchronization (QCS) protocol of Jozsa et. al.[1], which assumes a supply of such pure singlet states shared as a resource between the synchronizing parties Alice and Bob. Specifically, consider the unitary (Hadamard) transformation (π/2 -pulse followed by the spin operator σ z ) on H given byUnlike the states |0 and |1 , which are dark under time evolution (they only pick up an overall phase under U t ), the states |+ and |− are "clock states" (in other words, they accumulate an observable relative phase under U t ) because of the energy difference Ω as specified in Eq. (1). Such states can be used to "drive" precision clocks in the following way: Start, for example, with an ensemble of atoms in the state |+ produced by an initial Hadamard pulse at time t 0 , and apply a second Hadamard pulse at a later time t 0 + T . This leads to a final state ...

show abstract

Creation of entangled states of distant atoms by interference

Cited by 560 publications

References 24 publications

Phase-locked indistinguishable photons with synthesized waveforms from a solid-state source

Phase-locked indistinguishable photons with synthesized waveforms from a solid-state source

Co-designing a scalable quantum computer with trapped atomic ions

Lorentz-invariant look at quantum clock-synchronization protocols based on distributed entanglement

Contact Info

Product

Resources

About