A physical qubit with built-in error correction

Phys.org  February 2, 2024 To harness the potential of a quantum computer, quantum information must be protected against error by encoding it into a logical state that is suitable for quantum error correction. The Gottesman-Kitaev-Preskill (GKP) qubit is a promising candidate because the required multiqubit operations are readily available at optical frequency. An international team of researchers (Japan, Germany, Czech Republic, USA – University of Virginia) developed and verified a GKP state in propagating light at  telecommunication wavelength. The generation was based on interference of cat states, followed by homodyne measurements. Their final states exhibited nonclassicality and non-Gaussianity, including the […]

Superconducting qubit foundry accelerates progress in quantum research

MIT News  July 5, 2023 Sponsored by the Laboratory for Physical Sciences (LPS) Qubit Collaboratory, a National Quantum Initiative-funded center, the program makes MIT Lincoln Laboratory’s cutting-edge fabrication capabilities available at no cost to institutions working on U.S. government-funded research. Researchers can submit quantum circuit designs for fabrication, and the completed circuits are returned to advance scientific inquiry in their home facilities. The qubits are made on-site at the Microelectronics Laboratory, considered to be one of the U.S. government’s most advanced foundries, and in specialized prototyping facilities. More than 20 research groups are poised to leverage the foundry as the […]

Fluxonium Qubit Retains Information For 1.43 Milliseconds – 10x Longer Than Before

Science Alert  July 6, 2023 An international team of researchers (USA- University of Maryland, Switzerland) has built a fluxonium qubit that could retain information for 1.43 milliseconds. The superconducting fluxonium qubit had uncorrected coherence time T∗2=1.48±0.13ms, exceeding the state of the art for transmons by an order of magnitude. The average gate fidelity was benchmarked at 0.99991(1). Even in the millisecond range, the coherence time was limited by material absorption and could be further improved with a more rigorous fabrication. According to the researchers their demonstration may be useful for suppressing errors in the next generation quantum processors… read more. […]

The ‘flip-flop’ qubit: Realization of a new quantum bit in silicon controlled by electric signals

Phys.org  February 13, 2023 The spins of atoms and atom-like systems are among the most coherent objects in which to store quantum information. However, the need to address them using oscillating magnetic fields hinders their integration with quantum electronic devices. An international team of researchers (Australia, Japan) circumvented this hurdle by operating a single-atom “flip-flop” qubit in silicon, where quantum information is encoded in the electron-nuclear states of a phosphorus donor. The qubit was controlled using local electric fields at microwave frequencies, produced within a mos device. The electrical drive was mediated by the modulation of the electron-nuclear hyperfine coupling, […]

Electron pairing in quantum dots as a new approach to qubit research

Phys.org  November 25, 2022 Materials with intrinsic p-wave superconductivity, hosting Cooper pairs made of equal-spin electrons, have not been conclusively identified, nor synthesized, despite promising progress. Instead, engineered platforms where s-wave superconductors are brought into contact with magnetic materials have shown convincing signatures of equal-spin pairing. Researchers in the Netherlands have directly measured equal-spin pairing between spin-polarized quantum dots. The pairing is proximity-induced from an s-wave superconductor into a semiconducting nanowire with strong spin–orbit interaction. They demonstrated such pairing by showing that breaking a Cooper pair can result in two electrons with equal spin polarization. Their results demonstrated controllable detection […]

Stability in asymmetry: Scientists extend qubit lifetimes

Science Daily  October 13, 2022 An international team of researcher (US – University of Chicago, MIT, Northwestern University, Argonne National Laboratory, UK) demonstrated how the spin coherence in optically addressable molecular qubits can be controlled through engineering their host environment. By inserting chromium (IV)-based molecular qubits into a nonisostructural host matrix, they generated noise-insensitive clock transitions, through a transverse zero-field splitting, that are not present when using an isostructural host. This led to spin-coherence times of more than 10μs for optically addressable molecular spin qubits in a nuclear and electron-spin-rich environment. they modeled the dependence of spin coherence on transverse […]

Building a better quantum bit: New qubit breakthrough could transform quantum computing

Phys.org  May 4, 2022 A team of researchers in the US (Argonne National Laboratory, Lawrence Berkeley National Laboratory, research organization, MIT, University of Chicago, National High Magnetic Field Laboratory, Florida State University, Washington University) trapped an electron on an ultrapure solid neon surface in a vacuum. After building their platform, the team performed real-time qubit operations using microwave photons on a trapped electron and characterized its quantum properties. These tests demonstrated that solid neon provided a robust environment for the electron with very low electric noise to disturb it. By using a chip-scale superconducting resonator the team was able to […]

Qubits that operate at room temperature

Phys.org  March 17, 2020 Defect-based quantum systems are often complicated by charge-state instabilities and interference by phonons, which can diminish spin-initialization fidelities and limit room-temperature operation. An international team of researchers (Hungary, Sweden, USA – Argonne National Laboratory, University of Chicago, IBM, Russia) identified a pathway around these drawbacks by showing that an engineered quantum well can stabilize the charge state of a qubit. They constructed a model for previously unattributed point defect centers in silicon carbide as a near-stacking fault axial divacancy and show how this model explains these defects’ robustness against photoionization and room temperature stability. These results […]

Uncovering the hidden “noise” that can kill qubits

MIT News  September 16, 2019 Statistics-based models to estimate the impact of unwanted noise sources surrounding qubits to create new ways to protect them generally capture simplistic Gaussian noise. A team of researchers (MIT, Dartmouth College) developed a technique to separate non-Gaussian noise from the background Gaussian noise, and then used signal-processing techniques to reconstruct highly detailed information about those noise signals. The key innovation behind the work is carefully engineering the pulses to act as specific filters that extract properties of the “bispectrum,” a two-dimension representation that gives information about distinctive time correlations of non-Gaussian noise. Those reconstructions can […]

Researchers build transistor-like gate for quantum information processing — with qudits

EurekAlert  July 16, 2019 A team of researchers in the US (Purdue University, Oak Ridge National Laboratory) implemented qudit gate with a set of standard off-the-shelf equipment used daily in the optical communication industry. Qudits exist in multiple states, such as 0 and 1 and 2. More states mean that more data can be encoded and processed. They achieved more entanglement with fewer photons by encoding one qudit in the time domain and the other in the frequency domain of each of the two photons. They built a gate using the two qudits encoded in each photon, for a total […]