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Helsen, J. (author), Wallman, Joel J. (author), Flammia, Steven T. (author), Wehner, S.D.C. (author)Randomized benchmarking (RB) is an efficient and robust method to characterize gate errors in quantum circuits. Averaging over random sequences of gates leads to estimates of gate errors in terms of the average fidelity. These estimates are isolated from the state preparation and measurement errors that plague other methods such as channel...journal article 2019
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Woods, M.P. (author), Ng, N.H.Y. (author), Wehner, S.D.C. (author)Sadi Carnot's theorem regarding the maximum efficiency of heat engines is considered to be of fundamental importance in thermodynamics. This theorem famously states that the maximum efficiency depends only on the temperature of the heat baths used by the engine, but not on the specific structure of baths. Here, we show that when the heat...journal article 2019
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Dahlberg, E.A. (author), Wehner, S.D.C. (author)Stabilizer states form an important class of states in quantum information, and are of central importance in quantum error correction. Here, we provide an algorithm for deciding whether one stabilizer (target) state can be obtained from another stabilizer (source) state by single-qubit Clifford operations (LC), single-qubit Pauli measurements...journal article 2018
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Li, R. (author), Petit, L. (author), Franke, D.P. (author), Dehollain Lorenzana, J.P. (author), Helsen, J. (author), Steudtner, M. (author), Thomas, Nicole K. (author), Wehner, S.D.C. (author), Vandersypen, L.M.K. (author), Veldhorst, M. (author)The spin states of single electrons in gate-defined quantum dots satisfy crucial requirements for a practical quantum computer. These include extremely long coherence times, high-fidelity quantum operation, and the ability to shuttle electrons as a mechanism for on-chip flying qubits. To increase the number of qubits to the thousands or...journal article 2018
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Helsen, J. (author), Wallman, Joel J. (author), Wehner, S.D.C. (author)The q-qubit Clifford group, that is, the normalizer of the q-qubit Pauli group in U(2<sup>q</sup>), is a fundamental structure in quantum information with a wide variety of applications. We characterize all irreducible subrepresentations of the two-copy representation φ<sup>⊗2</sup> of the Clifford group on the two-fold tensor product of the...journal article 2018
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Rozpedek, F.D. (author), Schiet, Thomas (author), Lê, P.T. (author), Elkouss Coronas, D. (author), Doherty, Andrew C. (author), Wehner, S.D.C. (author)The goal of entanglement distillation is to turn a large number of weakly entangled states into a smaller number of highly entangled ones. Practical entanglement distillation schemes offer a trade-off between the fidelity to the target state and the probability of successful distillation. Exploiting such trade-offs is of interest in the...journal article 2018
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Helsen, J. (author), Steudtner, M. (author), Veldhorst, M. (author), Wehner, S.D.C. (author)A central challenge for the scaling of quantum computing systems is the need to control all qubits in the system without a large overhead. A solution for this problem in classical computing comes in the form of so-called crossbar architectures. Recently we made a proposal for a large-scale quantum processor (Li et al arXiv:1711.03807 (2017))...journal article 2018
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Rozpedek, F.D. (author), Goodenough, K.D. (author), Ribeiro, J.D. (author), Kalb, N. (author), Caprara Vivoli, V. (author), Reiserer, A.A. (author), Hanson, R. (author), Wehner, S.D.C. (author), Elkouss Coronas, D. (author)Quantum key distribution allows for the generation of a secret key between distant parties connected by a quantum channel such as optical fibre or free space. Unfortunately, the rate of generation of a secret key by direct transmission is fundamentally limited by the distance. This limit can be overcome by the implementation of so-called...journal article 2018
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Ribeiro, J.D. (author), Murta Guimarães, G. (author), Wehner, S.D.C. (author)We present a security analysis of conference key agreement (CKA) in the most adversarial model of device independence (DI). Our protocol can be implemented by any experimental setup that is capable of performing Bell tests [specifically, the Mermin-Ardehali-Belinskii-Klyshko (MABK) inequality], and security can in principle be obtained for...journal article 2018
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Wehner, S.D.C. (author), Elkouss Coronas, D. (author), Hanson, R. (author)The internet-a vast network that enables simultaneous long-range classical communication-has had a revolutionary impact on our world. The vision of a quantum internet is to fundamentally enhance internet technology by enabling quantum communication between any two points on Earth. Such a quantum internet may operate in parallel to the...review 2018
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Lipinska, V. (author), Murta Guimarães, G. (author), Wehner, S.D.C. (author)We consider the task of anonymously transmitting a quantum message in a network. We present a protocol that accomplishes this task using the W state and we analyze its performance in a quantum network where some form of noise is present. We then compare the performance of our protocol with some of the existing protocols developed for the task...journal article 2018
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Furrer, Fabian (author), Gehring, Tobias (author), Schaffner, Christian (author), Pacher, Christoph (author), Schnabel, Roman (author), Wehner, S.D.C. (author)Cryptographic protocols are the backbone of our information society. This includes two-party protocols which offer protection against distrustful players. Such protocols can be built from a basic primitive called oblivious transfer. We present and experimentally demonstrate here a quantum protocol for oblivious transfer for optical continuous...journal article 2018
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Dahlberg, E.A. (author), Wehner, S.D.C. (author)We introduce a simulator of a quantum internet with the specific goal to support software development. A quantum internet consists of local quantum processors, which are interconnected by quantum communication channels that enable the transmission of qubits between the different processors. While many simulators exist for local quantum...journal article 2018
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Riedel, Max F. (author), Bloch, Immanuel (author), Debuisschert, Thierry (author), Wilhelm-Mauch, Frank (author), Pruneri, Valerio (author), Vitanov, Nikolay V. (author), Wehner, S.D.C. (author), Calarco, Tommaso (author)The European Quantum Flagship is a 10-year, 1 billion Euro initiative, expected to bring quantum technologies from the lab to the market. The initiative is now taking off: The implementation and governance models are decided and the first research projects are commencing their work.journal article 2018
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Coles, Patrick J. (author), Berta, Mario (author), Tomamichel, Marco (author), Wehner, S.D.C. (author)Heisenberg's uncertainty principle forms a fundamental element of quantum mechanics. Uncertainty relations in terms of entropies were initially proposed to deal with conceptual shortcomings in the original formulation of the uncertainty principle and, hence, play an important role in quantum foundations. More recently, entropic uncertainty...journal article 2017
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Ng, N.H.Y. (author), Woods, M.P. (author), Wehner, S.D.C. (author)A suitable way of quantifying work for microscopic quantum systems has been constantly debated in the field of quantum thermodynamics. One natural approach is to measure the average increase in energy of an ancillary system, called the battery, after a work extraction protocol. The quality of energy extracted is usually argued to be good by...journal article 2017
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Rozpedek, F.D. (author), Kaniewski, J. (author), Coles, Patrick J. (author), Wehner, S.D.C. (author)The quantum uncertainty principle famously predicts that there exist measurements that are inherently incompatible, in the sense that their outcomes cannot be predicted simultaneously. In contrast, no such uncertainty exists in the classical domain, where all uncertainty results from ignorance about the exact state of the physical system....journal article 2017
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van Dam, S.B. (author), Humphreys, P.C. (author), Rozpedek, F.D. (author), Wehner, S.D.C. (author), Hanson, R. (author)Quantum networks distributed over distances greater than a few kilometres will be limited by the time required for information to propagate between nodes. We analyse protocols that are able to circumvent this bottleneck by employing multi-qubit nodes and multiplexing. For each protocol, we investigate the key network parameters that determine...journal article 2017
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Van Der Meer, Remco (author), Ng, N.H.Y. (author), Wehner, S.D.C. (author)In the study of thermodynamics for nanoscale quantum systems, a family of quantities known as generalized free energies have been derived as necessary and sufficient conditions that govern state transitions. These free energies become important especially in the regime where the system of interest consists of only a few (quantum) particles....journal article 2017
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Pfister, C. (author), Kaniewski, J. (author), Tomamichel, M. (author), Mantri, A. (author), Schmucker, R. (author), McMahon, N. (author), Milburn, G. (author), Wehner, S.D.C. (author)Quantum mechanics and the theory of gravity are presently not compatible. A particular question is whether gravity causes decoherence. Several models for gravitational decoherence have been proposed, not all of which can be described quantum mechanically. Since quantum mechanics may need to be modified, one may question the use of quantum...journal article 2016