Topic
Qubit
About: Qubit is a research topic. Over the lifetime, 29978 publications have been published within this topic receiving 723084 citations. The topic is also known as: quantum bit & qbit.
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TL;DR: The operation of a superconducting phase qudit with a number of levels d up to d = 5 is demonstrated and how to manipulate and measure the qudit state is shown, including simultaneous control of multiple transitions.
Abstract: At the heart of a quantum computer is the device on which information is to be encoded. This is typically done with a qubit, a two-level quantum system analogous to the two-level bit that encodes 0 and 1 in classical computers. However, there need not be just two quantum energy levels. There could be three (a qutrit), or more generally, d -levels (a qudit) in the device. Neeley et al. (p. [722][1]; see the Perspective by [Nori][2] ) demonstrate a five-level quantum device and show that their qudit can be used to emulate the processes involved in manipulating quantum spin. The use of multilevel qudits may also have potential in quantum information processing by simplifying certain computational tasks and simplifying the circuitry required to realize the quantum computer itself.
[1]: /lookup/volpage/325/722
[2]: /lookup/doi/10.1126/science.1178828
274 citations
TL;DR: In this article, an error mitigation protocol was proposed to mitigate single-and two-qubit experiments on a superconducting quantum processor, with no additional hardware modifications, with the aim of enhancing the computational capability of the processor.
Abstract: Quantum computation, a completely different paradigm of computing, benefits from theoretically proven speed-ups for certain problems and opens up the possibility of exactly studying the properties of quantum systems. Yet, because of the inherent fragile nature of the physical computing elements, qubits, achieving quantum advantages over classical computation requires extremely low error rates for qubit operations as well as a significant overhead of physical qubits, in order to realize fault-tolerance via quantum error correction. However, recent theoretical work has shown that the accuracy of computation based off expectation values of quantum observables can be enhanced through an extrapolation of results from a collection of varying noisy experiments. Here, we demonstrate this error mitigation protocol on a superconducting quantum processor, enhancing its computational capability, with no additional hardware modifications. We apply the protocol to mitigate errors on canonical single- and two-qubit experiments and then extend its application to the variational optimization of Hamiltonians for quantum chemistry and magnetism. We effectively demonstrate that the suppression of incoherent errors helps unearth otherwise inaccessible accuracies to the variational solutions using our noisy processor. These results demonstrate that error mitigation techniques will be critical to significantly enhance the capabilities of near-term quantum computing hardware.
274 citations
TL;DR: The production of photon fields with a fixed photon number on demand is discussed based on a cavity quantum electrodynamics scheme using the strong coupling between excited atoms and a single-mode cavity field.
Abstract: Many applications in quantum information or quantum computing require radiation with a fixed number of photons. This increased the demand for systems able to produce such fields. We discuss the production of photon fields with a fixed photon number on demand. The first experimental demonstration of the device is described. This setup is based on a cavity quantum electrodynamics scheme using the strong coupling between excited atoms and a single-mode cavity field.
274 citations
TL;DR: This work shows how to employ spectrally multiplexed states and memories with fixed storage times that allow such mapping between spectral modes, and demonstrates storage followed by the required feed-forward-controlled frequency manipulation.
Abstract: Future multiphoton applications of quantum optics and quantum information science require quantum memories that simultaneously store many photon states, each encoded into a different optical mode, and enable one to select the mapping between any input and a specific retrieved mode during storage. Here we show, with the example of a quantum repeater, how to employ spectrally multiplexed states and memories with fixed storage times that allow such mapping between spectral modes. Furthermore, using a $\mathrm{Ti}:\mathrm{Tm}:{\mathrm{LiNbO}}_{3}$ waveguide cooled to 3 K, a phase modulator, and a spectral filter, we demonstrate storage followed by the required feed-forward-controlled frequency manipulation with time-bin qubits encoded into up to 26 multiplexed spectral modes and 97% fidelity.
273 citations
TL;DR: In this paper, a ten-qubit system based on spins in impure diamond achieves coherence times of over a minute, which is the fastest known coherence time for a ten qubit system.
Abstract: A ten-qubit system based on spins in impure diamond achieves coherence times of over a minute.
272 citations