9 research outputs found
Quantum repeaters based on individual electron spins and nuclear-spin-ensemble memories in quantum dots
Inspired by recent developments in the control and manipulation of quantum
dot nuclear spins, which allow for the transfer of an electron spin state to
the surrounding nuclear-spin ensemble for storage, we propose a quantum
repeater scheme that combines individual quantum dot electron spins and
nuclear-spin ensembles, which serve as spin-photon interfaces and quantum
memories respectively. We consider the use of low-strain quantum dots embedded
in high-cooperativity optical microcavities. Quantum dot nuclear-spin ensembles
allow for the long-term storage of entangled states, and heralded entanglement
swapping is performed using cavity-assisted gates. We highlight the advances in
quantum dot technologies required to realize our quantum repeater scheme which
promises the establishment of high-fidelity entanglement over long distances
with a distribution rate exceeding that of the direct transmission of photons.Comment: 21 pages, 5 figure
Quantum Optical Memory for Entanglement Distribution
Optical photons are powerful carriers of quantum information, which can be
delivered in free space by satellites or in fibers on the ground over long
distances. Entanglement of quantum states over long distances can empower
quantum computing, quantum communications, and quantum sensing. Quantum optical
memories can effectively store and manipulate quantum states, which makes them
indispensable elements in future long-distance quantum networks. Over the past
two decades, quantum optical memories with high fidelity, high efficiencies,
long storage times, and promising multiplexing capabilities have been
developed, especially at the single photon level. In this review, we introduce
the working principles of commonly used quantum memory protocols and summarize
the recent advances in quantum memory demonstrations. We also offer a vision
for future quantum optical memory devices that may enable entanglement
distribution over long distances
QEYSSat 2.0 -- White Paper on Satellite-based Quantum Communication Missions in Canada
We present the white paper developed during the QEYSSat 2.0 study, which was
undertaken between June 2021 and March 2022. The study objective was to
establish a technology road-map for a Canada-wide quantum network enabled by
satellites. We survey the state-of-art in quantum communication technologies,
identify the main applications and architectures, review the technical
readiness levels and technology bottlenecks and identify a future mission
scenario. We report the findings of a dedicated one-day workshop that included
Canadian stakeholders from government, industry and academia to gather inputs
and insights for the applications and technical road-map. We also provide an
overview of the Quantum EncrYption and Science Satellite (QEYSSat) mission
expected to launch in 2024-2025 and its anticipated outcomes. One of the main
outcomes of this study is that developing the main elements for a Canada-wide
quantum internet will have the highest level of impact, which includes
Canada-wide entanglement distribution and teleportation. We present and analyze
a possible future mission ('QEYSSat 2.0') that would enable a long range
quantum teleportation across Canada as an important step towards this vision.Comment: 108 pages, 38 figures, white paper to be submitted to CJ
Long-distance quantum communication with single solid-state spins
Long-distance transfer of quantum information is an essential ability for many applications of quantum science. A natural choice to distribute quantum information is to encode it into photons and transfer it through optical fibers. However, due to the unavoidable transmission losses present in every communication channel, the distances for efficient quantum communication via direct-state transfer are limited to a few hundred kilometers. To overcome this limitation, the use of quantum repeaters has been suggested. A quantum repeater protocol aims to establish entanglement (i.e., quantum correlation) between remote nodes by first generating entanglement over shorter distance pieces, storing it in quantum memories, and finally extending it to the whole distance using entanglement swapping. The main goal of this thesis is to design quantum repeater architectures using single solid-state quantum emitters and to develop the two-qubit gates required for performing entanglement swapping. We first explain the basic ideas of quantum repeaters and introduce potential material candidates, single erbium (168Er) and europium (151Eu) ions doped yttrium orthosilicate photonic crystals. Next, we propose a quantum repeater scheme combing erbium and europium ions to generate and distribute entanglement over long distances. We study the entanglement generation rate of the protocol and compare it with the rate of a well-known ensemble-based quantum repeater. Then, using cavity assisted interactions, we propose three different schemes to perform high fidelity two-qubit gates between single quantum systems. We quantify their expected performance in detail by taking into account many realistic imperfections and compare their strengths and weaknesses. The ability to perform local two-qubits gates is especially crucial in terms of distributing entanglement. Finally, based on our gained knowledge through these projects, we propose our second quantum repeater architecture based on erbium (167Er) ions, which outperforms the first scheme. We study two possibilities for distributing entanglement and calculate the overall fidelity as well as the distribution rate of the protocol
Proposal for transduction between microwave and optical photons using -doped yttrium orthosilicate
Efficient transduction devices that reversibly convert optical and microwave
quantum signals into each other are essential for integrating different
technologies. Rare-earth ions in solids, and in particular Erbium ions, with
both optical and microwave addressable transitions are promising candidates for
designing transducers. We propose a microwave-to-optical quantum transducer
scheme based on the dark state protocol in doped into
yttrium orthosilicate (YSO) at zero external magnetic fields. Zero-field
operation is beneficial for superconducting resonators that can incur extra
losses in magnetic fields. By calculating the fidelity and efficiency of the
transducer, considering the most important imperfections, we show that an
efficient conversion is possible with a high fidelity. We also investigate the
microwave transitions of :YSO that can be used for the
transducer protocol.Comment: 8 pages, 5 figure
Proposal for room-temperature quantum repeaters with nitrogen-vacancy centers and optomechanics
We propose a quantum repeater architecture that can operate under ambient
conditions. Our proposal builds on recent progress towards non-cryogenic
spin-photon interfaces based on nitrogen-vacancy centers, which have excellent
spin coherence times even at room temperature, and optomechanics, which allows
to avoid phonon-related decoherence and also allows the emitted photons to be
in the telecom band. We apply the photon number decomposition method to
quantify the fidelity and the efficiency of entanglement established between
two remote electron spins. We describe how the entanglement can be stored in
nuclear spins and extended to long distances via quasi-deterministic
entanglement swapping operations involving the electron and nuclear spins. We
furthermore propose schemes to achieve high-fidelity readout of the spin states
at room temperature using the spin-optomechanics interface. Our work shows that
long-distance quantum networks made of solid-state components that operate at
room temperature are within reach of current technological capabilities.Comment: arXiv admin note: substantial text overlap with arXiv:2012.0668
Memory and Transduction Prospects for Silicon T Center Devices
The T center, a silicon-native spin-photon interface with telecommunication-band optical transitions and long-lived microwave qubits, offers an appealing new platform for both optical quantum memory and microwave-to-optical telecommunication-band transduction. A wide range of quantum memory and transduction schemes could be implemented withT center ensembles with sufficient optical depth, with advantages and disadvantages that depend sensitively on the ensemble properties. In this work we characterize T center spin ensembles to inform device design. We perform the first T ensemble optical depth measurement and calculate the improvement in center density or resonant optical enhancement required for efficient optical quantum memory. We further demonstrate a coherent microwave interface by coherent population trapping and Autler-Townes splitting. We then determine the most promising microwave and optical quantum memory protocol for such ensembles. By estimating the memory efficiency both in free space and in the presence of a cavity, we show that efficient optical memory is possible with reasonable optical density forecasts. Finally, we formulate a transduction proposal and discuss the achievable efficiency and fidelity
Topical White Paper:A Case for Quantum Memories in Space
It has recently been theoretically shown that Quantum Memories (QM) could enable truly global quantum networking when deployed in space thereby surpassing the limited range of land-based quantum repeaters. Furthermore, QM in space could enable novel protocols and long-range entanglement and teleportation applications suitable for Deep-Space links and extended scenarios for fundamental physics tests. In this white paper we will make the case for the importance of deploying QMs to space, and also discuss the major technical milestones and development stages that will need to be considered