Entanglement of single-atom quantum bits at a distance

Moehring, D. L.; Maunz, Peter; Olmschenk, S.; Younge, K. C.; Matsukevich, Dzmitry; Duan, Luming; Monroe, Christopher

doi:10.1038/nature06118

Cited by 792 publications

(791 citation statements)

References 30 publications

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“…A natural extension of the quantum teleportation protocol is to entangle the spin states of two distant QDs that have never directly interacted with each other 44,45 . To entangle two spins one would replace the photonic qubit with a photon that is entangled with another QD spin: a coincidence detection at the output of the HOM interferometer, in this case, heralds successful generation of entanglement between the two distant spins.…”

Section: Discussionmentioning

confidence: 99%

Quantum teleportation from a propagating photon to a solid-state spin qubit

et al. 2013

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A quantum interface between a propagating photon used to transmit quantum information and a long-lived qubit used for storage is of central interest in quantum information science. A method for implementing such an interface between dissimilar qubits is quantum teleportation. Here we experimentally demonstrate transfer of quantum information carried by a photon to a semiconductor spin using quantum teleportation. In our experiment, a single photon in a superposition state is generated using resonant excitation of a neutral dot. To teleport this photonic qubit, we generate an entangled spin-photon state in a second dot located 5 m away and interfere the photons from the two dots in a Hong-Ou-Mandel set-up. Thanks to an unprecedented degree of photon-indistinguishability, a coincidence detection at the output of the interferometer heralds successful teleportation, which we verify by measuring the resulting spin state after prolonging its coherence time by optical spin-echo.

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Section: Discussionmentioning

confidence: 99%

Quantum teleportation from a propagating photon to a solid-state spin qubit

et al. 2013

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“…When photons collected from two separate communication qubits are mode-matched and interfered on a 50/50 beamsplitter (Figure 2d), coincident detection of single photons on the output modes of the beamsplitter herald a Bell-state of the photons and thus the creation of entanglement between the memory qubits through entanglement swapping. 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.).…”

Section: Ion Trap Qubits and Wiresmentioning

confidence: 99%

Co-designing a scalable quantum computer with trapped atomic ions

2016

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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...

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“…Indeed, an elementary quantum network consisting of ions in two traps a few meters apart, has been entangled via travelling ultraviolet photons [7]. A challenge is that most readily-accessible photonic transitions in trapped ions lie at wavelengths that suffer significant absorption loss in materials for manipulating and guiding light, thereby limiting the internode networking distance.…”

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Polarisation-preserving photon frequency conversion from a trapped-ion-compatible wavelength to the telecom C-band

et al. 2017

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Given the great success in encoding, manipulating, storing and reading-out quantum information in their electronic states, trapped atomic ions represent a powerful platform with which to build, or integrate into, the nodes of quantum networks [5,6]. Indeed, an elementary quantum network consisting of ions in two traps a few meters apart, has been entangled via travelling ultraviolet photons [7]. A challenge is that most readily-accessible photonic transitions in trapped ions lie at wavelengths that suffer significant absorption loss in materials for manipulating and guiding light, thereby limiting the internode networking distance. Another challenge is that ionic transitions are fixed and narrowband, such that, except in rare cases [8], they cannot be interfaced with other examples of quantum matter to enable new ion-hybrid quantum systems [9]. Note that frequency-distinguishable quantum systems can be linked via their photons, though at the cost of reducing the efficiency of making that link [10].The aforementioned challenges could be overcome using quantum frequency conversion (QFC) [11,12]; a nonlinear optical process in which a photon of one frequency is converted to another, whilst preserving all the quantum and classical photon properties. QFC of single photons has recently been studied in a variety of contexts [13][14][15][16][17][18] and is typically achieved using three-wave mixing in a secondorder non-linear ( 2 ) crystal. It has been shown that QFC can preserve a broad range of photon properties, including first-and second-order coherence, and pre-existing photonphoton entanglement [12,19,20]. QFC could, therefore, act as a quantum photonic adapter for trapped ions, allowing their high-energy photonic transitions to be interfaced with the lower-energy photons better suited for long-distance travel through optical fibers, or with other forms of quantum matter.Interfacing trapped ions with the telecom wavelengths of 1310 nm (O band) or 1550 nm (C band) is particularly Abstract We demonstrate polarisation-preserving frequency conversion of single-photon-level light at 854 nm, resonant with a trapped-ion transition and qubit, to the 1550-nm telecom C band. A total photon in / fiber-coupled photon out efficiency of ∼30% is achieved, for a free-running photon noise rate of ∼60 Hz. This performance would enable telecom conversion of 854 nm polarisation qubits, produced in existing trapped-ion systems, with a signal-to-noise ratio greater than 1. In combination with near-future trappedion systems, our converter would enable the observation of entanglement between an ion and a photon that has travelled more than 100 km in optical fiber: three orders of magnitude further than the state-of-the-art.

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Entanglement of single-atom quantum bits at a distance

Cited by 792 publications

References 30 publications

Quantum teleportation from a propagating photon to a solid-state spin qubit

Quantum teleportation from a propagating photon to a solid-state spin qubit

Co-designing a scalable quantum computer with trapped atomic ions

Polarisation-preserving photon frequency conversion from a trapped-ion-compatible wavelength to the telecom C-band

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