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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-KitaevPreskill (GKP) qubit is a promising candidate because the required multiqubit operations are readily available at optical frequency. To date, however, GKP qubits have been demonstrated only at mechanical and microwave frequencies. We realized a GKP state in propagating light at telecommunication wavelength and verified it through homodyne measurements without loss corrections. The generation is based on interference of cat states, followed by homodyne measurements. Our final states exhibit nonclassicality and non-Gaussianity, including the trident shape of faint instances of GKP states. Improvements toward brighter, multipeaked GKP qubits will be the basis for quantum computation with light. [ABSTRACT FROM AUTHOR]

The article discusses Australia's significant investment in PsiQuantum to build a large-scale quantum computing facility in Brisbane, Queensland, focusing on the country's gamble on photon-based quantum computing technology. Topics include the advantages of photon-based qubits over traditional approaches, the challenges and advancements in scaling up this technology, and the potential impact of Australia's investment on its quantum computing ecosystem and workforce development.

Quantum walks are the quantum mechanical analog of classical random walks and an extremely powerful tool in quantum simulations, quantum search algorithms, and even for universal quantum computing. In our work, we have designed and fabricated an 8-by-8 two-dimensional square superconducting qubit array composed of 62 functional qubits. We used this device to demonstrate high-fidelity single- and two-particle quantum walks. Furthermore, with the high programmability of the quantum processor, we implemented a Mach-Zehnder interferometer where the quantum walker coherently traverses in two paths before interfering and exiting. By tuning the disorders on the evolution paths, we observed interference fringes with single and double walkers. Our work is a milestone in the field, bringing future larger-scale quantum applications closer to realization for noisy intermediate-scale quantum processors. [ABSTRACT FROM AUTHOR]

The article focuses on a new quantum algorithm proposed by computer scientist Oded Regev, which could potentially be more efficient than Peter Shor's 30-year-old algorithm for factoring large numbers, a critical task for hacking internet encryption. Topics discussed include the multidimensional nature of Regev's algorithm, its potential to reduce the number of gates required, and the drawbacks associated with increased memory requirements, which raise questions about its practicality.

Large-scale quantum computers will require quantum gate operations between widely separated qubits. A method for implementing such operations, known as quantum gate teleportation (QGT), requires only local operations, classical communication, and shared entanglement. We demonstrate QGT in a scalable architecture by deterministically teleporting a controlled-NOT (CNOT) gate between two qubits in spatially separated locations in an ion trap. The entanglement fidelity of our teleported CNOT is in the interval (0.845, 0.872) at the 95% confidence level. The implementation combines ion shuttling with individually addressed single-qubit rotations and detections, same- and mixed-species two-qubit gates, and real-time conditional operations, thereby demonstrating essential tools for scaling trapped-ion quantum computers combined in a single device. [ABSTRACT FROM AUTHOR]

A key step toward demonstrating a quantum system that can address difficult problems in physics and chemistry will be performing a computation beyond the capabilities of any classical computer, thus achieving so-called quantum supremacy. In this study, we used nine superconducting qubits to demonstrate a promising path toward quantum supremacy. By individually tuning the qubit parameters, we were able to generate thousands of distinct Hamiltonian evolutions and probe the output probabilities. The measured probabilities obey a universal distribution, consistent with uniformly sampling the full Hilbert space. As the number of qubits increases, the system continues to explore the exponentially growing number of states. Extending these results to a system of 50 qubits has the potential to address scientific questions that are beyond the capabilities of any classical computer. [ABSTRACT FROM AUTHOR]

The article presents insights on the increasing popularity of quantum computing. Topics discussed include the efforts of small business enterprises and international businesses to harness quantum mechanics for use in quantum computers, the difference between a classical computer and a quantum computer, and the negative characteristic of quantum superpositions. Also mentioned are the quantum bits or qubits being experimented by companies which include trapped ions and superconducting loops.

The article presents the discussion on Quantum computers (QCs) exponentially speeding up a number of problems in optimization, materials science, and chemistry. Topics include increasing millions of qubits for quantum error correction; background for the solid-state spin qubit provided by creating few-electron quantum dots in 2D electron gas (2DEG) structures; and stating a conducting channel inside the energy gap consisting of a ground state.

The construction of a quantum computer remains a fundamental scientific and technological challenge because of the influence of unavoidable noise. Quantum states and operations can be protected from errors through the use of protocols for quantum computing with faulty components. We present a quantum error-correcting code in which one qubit is encoded in entangled states distributed over seven trapped-ion qubits. The code can detect one bit flip error, one phase flip error, or a combined error of both, regardless on which of the qubits they occur. We applied sequences of gate operations on the encoded qubit to explore its computational capabilities. This seven-qubit code represents a fully functional instance of a topologically encoded qubit, or color code, and opens a route toward fault-tolerant quantum computing. [ABSTRACT FROM AUTHOR]

Trapped atomic ions are standards for quantum information processing, serving as quantum memories, hosts of quantum gates in quantum computers and simulators, and nodes of quantum communication networks. Quantum bits based on trapped ions enjoy a rare combination of attributes: They have exquisite coherence properties, they can be prepared and measured with nearly 100% efficiency, and they are readily entangled with each other through the Coulomb interaction or remote photonic interconnects. The outstanding challenge is the scaling of trapped ions to hundreds or thousands of qubits and beyond, at which scale quantum processors can outperform their classical counterparts in certain applications. We review the latest progress and prospects in that effort, with the promise of advanced architectures and new technologies, such as microfabricated ion traps and integrated photonics. [ABSTRACT FROM AUTHOR]

Stable quantum bits, capable both of storing quantum information for macroscopic time scales and of integration inside small portable devices, are an essential building block for an array of potential applications. We demonstrate high-fidelity control of a solid-state qubit, which preserves its polarization for several minutes and features coherence lifetimes exceeding 1 second at room temperature. The qubit consists of a single 13C nuclear spin in the vicinity of a nitrogen-vacancy color center within an isotopically purified diamond crystal. The long qubit memory time was achieved via a technique involving dissipative decoupling of the single nuclear spin from its local environment. The versatility, robustness, and potential scalability of this system may allow for new applications in quantum information science. [ABSTRACT FROM AUTHOR]

Quantum computers have the potential to solve certain problems faster than classical computers. To exploit their power, it is necessary to perform interqubit operations and generate entangled states. Spin qubits are a promising candidate for implementing a quantum processor because of their potential for scalability and miniaturization. However, their weak interactions with the environment, which lead to their long coherence times, make interqubit operations challenging. We performed a controlled two-qubit operation between singlet-triplet qubits using a dynamically decoupled sequence that maintains the two-qubit coupling while decoupling each qubit from its fluctuating environment. Using state tomography, we measured the full density matrix of the system and determined the concurrence and the fidelity of the generated state, providing proof of entanglement. [ABSTRACT FROM AUTHOR]

The article discusses the creation of benchmarks and metrics to measure the progress of quantum computers. Topics include challenges associated with comparing the diverse designs of relatively rudimentary quantum computers as of 2019, quantum computers' reliability on qubits to compute, and the metric of quantum supremacy which indicates the ability of quantum computers to solve problems that conventional computers cannot.

The article discusses research on the use of vibrations to control quantum circuits. Topics include the use of qubits in quantum computing, differences between a microwave resonator and a mechanical or acoustic resonator, and the use of surface acoustic waves (SAWs). The possible significance of quantum acoustics is addressed.

The article reports on the quantum computing company D-Wave Systems' development of a quantum processor, or computer, referred to as the D-Wave machine; the quantum chip of which holds 1,152 qubits.

The article discusses a quantum computer from quantum computing company D-Wave Systems, called the D-Wave computer. Topics include tests of a D-Wave computer owned by aerospace firm Lockheed Martin by physicist Matthias Troyer at the Swiss Federal Institute of Technology in Zurich and physicist Daniel Lidar at the University of Southern California in Los Angeles that found it computed no faster than conventional computers, D-Wave’s quantum annealing technique, and qubits.

The article discusses reports within the issue by M. Steger and team and P. C. Maurer and colleagues on the development of solid-state quantum memory based on nuclear spin states. Various aspects of quantum information processing are presented, including quantum qubit initialization, the quality and duration of quantum memories, and the hyperfine interaction process of decoupling the electron qubit to the nuclear-spin. Also explored is the improvement of silicon-phosphorus qubit coherence through optical ionization of the phosphorus donor.