A new design for quantum computers

Science Daily  February 15, 2024 Arrays of Rydberg atoms are suitable to study quantum phase transitions in one dimension. Theoretically predicted chiral transition out of period-four phase is still pending experimental verification mainly due to extremely short interval over which this transition is realized in a single-component Rydberg array. Researchers in the Netherlands showed that multicomponent Rydberg arrays with extra experimentally tunable parameters provided a mechanism to manipulate quantum critical properties without breaking translation symmetry explicitly. They considered an effective blockade model of two component Rydberg atoms. Weak and strong components obeyed nearest- and next-nearest-neighbor blockades correspondingly. When laser detuning […]

A simpler way to connect quantum computers

Science Daily  August 30, 2023 Recently, there has been significant interest in rare earth ions, in particular Er3+ for its telecom band optical transition that allows long-distance transmission in optical fibres. However, the development of repeater nodes based on rare earth ions has been hampered by optical spectral diffusion, precluding indistinguishable single-photon generation. Researchers at Princeton University implanted Er3+ into CaWO4 to realize significantly reduced optical spectral diffusion. For shallow implanted ions coupled to nanophotonic cavities with large Purcell factor, they observed single-scan optical linewidths of 150 kHz and long-term spectral diffusion of 63 kHz, both close to the Purcell-enhanced radiative linewidth […]

‘Toggle switch’ can help quantum computers cut through the noise

Science Daily  June 26, 2023 Qubits in cavity quantum electrodynamic (QED) architectures are often operated in the dispersive regime, in which the operating frequency of the cavity depends on the energy state of the qubit, and vice versa. The ability to tune these dispersive shifts provides additional options for performing either quantum measurements or logical manipulations. A team of researchers in the US (NIST- Boulder,CO, UMass Amherst, UMass Lowell, Raytheon, MA) coupled two transmon qubits to a lumped-element cavity through a shared superconducting quantum interference device (SQUID). The design balanced the mutual capacitive and inductive circuit components so that both […]

Qubits put new spin on magnetism: Boosting applications of quantum computers

Science Daily  March 17, 2023 Unveiling the fundamental dynamics of naturally or artificially formed magnetic quasicrystals in the presence of an external magnetic field remains a difficult problem that may have implications for the design of information processing devices. Researchers at Los Alamos National Laboratory embedded a qubit magnetic Penrose quasicrystal into a quantum annealer to reproduce the formation of magnetic phases driven by specific physical parameter selections. It allowed them to distinguish a wide range of frustrated magnetic configurations at the single-spin scale. They observed some spins dynamically activate, while others remained static, all within an average magnetization space […]

A new method for quantum computing

Phys.org  January 31, 2022 Using trapped-ion platform and optical tweezers researchers in the Netherlands have constructed new building blocks for quantum computing that pose fewer technical difficulties than current state-of-the art methods. Since the electric field allows for long-range qubit-qubit interactions mediated by the center-of-mass motion of the ion crystal alone, it is inherently scalable to large ion crystals. The proposed scheme does not rely on ground-state cooling. They studied the effects of imperfect cooling of the ion crystal, as well as the role of unwanted qubit-motion entanglement, and discuss the prospects of implementing the state-dependent tweezers in the laboratory… […]

Scientists simulate ‘fingerprint’ of noise on quantum computer

Phys.org  January 26, 2022 Traditionally, noise on the quantum device is characterized directly through qubit and gate measurements, but this approach has drawbacks as it does not adequately capture the effect of noise on realistic multi-qubit applications. A team of researchers in the US (University of Chicago, Purdue University) simulated the relaxation of stationary quantum states on a quantum computer to obtain a unique spectroscopic fingerprint of the computer’s noise. In contrast to traditional approaches, they obtained the frequency profile of the noise as it is experienced by the simulated stationary quantum states. Data from multiple superconducting-qubit IBM processors shows […]

Light meets superconducting circuits

EurekAlert  May 10, 2021 Realizing the full potential of quantum computers requires a significant increase in the number of qubits to store and manipulate quantum information. To prevent contaminating quantum signals by thermal noise, the superconducting quantum systems must operate at ultra-low temperatures. An international team of researchers (Switzerland, India) has developed a novel approach that uses light to read out superconducting circuits. They replaced low-noise high-electron mobility transistors and coaxial cables with a lithium niobate electro-optical phase modulator and optical fibers. Microwave signals from superconducting circuits modulate a laser carrier and encode information on the output light at cryogenic […]

Optical fiber could boost power of superconducting quantum computers

Science Daily  March 24, 2021 In superconducting quantum processors, each qubit is individually addressed with microwave signal lines that connect room-temperature electronics to the cryogenic environment of the quantum circuit. The complexity and heat load associated with the multiple coaxial lines per qubit limits the maximum possible size of a processor to a few thousand qubits. A team of researchers in the US (NIST, Boulder CO, University of Colorado) has introduced a photonic link using an optical fibre to guide modulated laser light from room temperature to a cryogenic photodetector, capable of delivering shot-noise-limited microwave signals directly at millikelvin temperatures. […]

Electrically switchable qubit can tune between storage and fast calculation modes

Science Daily  January 11, 2021 An international team of researchers (Switzerland, the Netherland) has created the qubits in the form of “hole spins” that can be switched from a stable idle mode to a fast calculation mode. The spins can be selectively coupled — via a photon, for example — to other spins by tuning their resonant frequencies. They can be coherently flipped from up to down in as little as a nanosecond allowing up to a billion switches per second. For their experiments, the researchers used a semiconductor nanowire made of silicon and germanium wire that has a diameter […]

New approach to circuit compression could deliver real-world quantum computers years ahead of schedule

EurekAlert  November 12, 2020 “Quantum advantage” has been achieved in Noisy Intermediate-Scale Quantum (NISQ) devices in early proof-of-principle experiments. But the NISQ devices are still prone to lots of errors that accumulate during their operation. To negate the need for millions of physical qubits for a fault-tolerant computer researchers in Japan proposed the use of the ZX-calculus as an intermediate language for braided circuit compression in large-scale fault-tolerant quantum computers. According to the researchers by compressing quantum circuits, they could reduce the size of the quantum computer and its runtime, which in turn lessens the requirement for error protection…read more. […]