Phys.org September 27, 2022 An international team of researchers (Sweden, Japan) has developed a technique to overcome to noise and interference in quantum systems. Their technique could create any of the previously demonstrated states and the cubic phase state. They used a sequence of interleaved selective number-dependent arbitrary phase (SNAP) gates and displacements. The state preparation was optimized in two steps – first they used a gradient-descent algorithm to optimize the parameters of the SNAP and displacement gates; then optimized the envelope of the pulses implementing the SNAP gates. The results showed that this way of creating highly nonclassical states […]
Tag Archives: Quantum computers
Characterizing the materials for next-generation quantum computers with nonlinear optical spectroscopy
Phys.org July 1, 2022 An international team of researchers (Germany, UC Irvine) developed a microscopic theory for the 2D spectroscopy of one-dimensional topological superconductors. They considered a ring geometry of an archetypal topological superconductor with periodic boundary conditions, bypassing energy-specific differences caused by topologically protected or trivial boundary modes that are hard to distinguish. They showed numerically and analytically that the cross-peak structure of the 2D spectra carries unique signatures of the topological phases of the chain. According to the researchers their work reveals how 2D spectroscopy can identify topological phases in bulk properties…read more. TECHNICAL ARTICLE
Theory suggests quantum computers should be exponentially faster on some learning tasks than classical machines
Phys.org June 10, 2022 An international team of researchers (USA – Catech, Harvard University, UC Berkeley, Google, Microsoft, Austria) has proved that quantum machines could learn from exponentially fewer experiments than the number required by conventional experiments. This exponential advantage is shown for predicting properties of physical systems, performing quantum principal component analysis, and learning about physical dynamics. The quantum resources needed for achieving an exponential advantage are quite modest in some cases. Conducting experiments with 40 superconducting qubits and 1300 quantum gates, they demonstrated that a substantial quantum advantage is possible with today’s quantum processors…read more. TECHNICAL ARTICLE 1 […]
Tiny materials lead to a big advance in quantum computing
MIT News January 27, 2022 An international team of researchers (USA – MIT, MIT Lincoln Laboratory, Japan) used hexagonal boron nitride to build a parallel-plate capacitor for a qubit. To fabricate the capacitor, they sandwiched hexagonal boron nitride between very thin layers of another van der Waals material, niobium diselenide and connected the capacitor to the existing structure and cooled the qubit to 20 millikelvins (-273.13 C). The resulting qubit was about 100 times smaller than what they made with traditional techniques on the same chip. The coherence time, or lifetime, of the qubit was only a few microseconds shorter […]
Crucial leap in error mitigation for quantum computers
Phys.org December 9, 2021 Coherent errors severely limit the performance of quantum algorithms in an unpredictable manner, and mitigating their impact is necessary for realizing reliable quantum computations. The average error rates measured by randomized benchmarking and related protocols are not sensitive to the full impact of coherent errors and therefore do not reliably predict the global performance of quantum algorithms. Randomized compiling is designed to overcome these performance limitations by converting coherent errors into stochastic noise, dramatically reducing unpredictable errors in quantum algorithms, and enabling accurate predictions of algorithmic performance from error rates measured via cycle benchmarking. An international […]
A new way to control qubits
Phys.org September 22, 2021 A team of researchers in the US (NIST, University of Colorado, Lawrence Livermore National Laboratory, University of Oregon, UT Austin) demonstrated high-fidelity laser-free universal control of two trapped-ion qubits by creating both symmetric and antisymmetric maximally entangled states with fidelities of 1+0−0.0017 and 0.9977+0.0010−0.0013, respectively (68 per cent confidence level), corrected for initialization error. They used a scheme based on radiofrequency magnetic field gradients combined with microwave magnetic fields that is robust against multiple sources of decoherence and usable with essentially any trapped ion species. The scheme has the potential to perform simultaneous entangling operations on […]
Quantum computing with holes
Phys.org June 3, 2021 An international team of researchers (Austria, Italy, Germany, Spain) has created a new candidate system for reliable qubits using the spin of holes which carry the quantum-mechanical property of spin and interact if they come close to each other. The hole can move around in the solid when a neighboring electron fills the hole. They confined the holes to the germanium-rich layer in the middle of layered silicon and germanium adding gates to control the movement of holes. They could move holes and alter their properties. By engineering different hole properties, they created the qubit out […]
Researchers create entangled photons 100 times more efficiently than previously possible
Phys.org December 17, 2020 Current methods of creating entanglement are inefficient, requiring a torrent of incoming laser light comprising hundreds of millions of photons before a single entangled photon pair will grudgingly drip out at the other end. Based on their earlier research, researchers at the Stevens Institute of Technology carved extremely high-quality racetrack-shaped microcavities into flakes of lithium niobate crystal. The cavities internally reflect photons with very little loss of energy, enabling light to circulate longer and interact with greater efficiency. By fine-tuning additional factors such as temperature, the team was able to create an unprecedentedly bright source of […]
Optical wiring for large quantum computers
Phy.org October 22, 2020 The fundamental qualities of individual trapped-ion qubits are promising for long-term systems, but the optics involved in their precise control are a barrier to scaling. Researchers in Switzerland used scalable optics co-fabricated with a surface-electrode ion trap to achieve high-fidelity multi-ion quantum logic gates, which are often the limiting elements in building up the precise, large-scale entanglement that is essential to quantum computation. Light is efficiently delivered to a trap chip in a cryogenic environment via direct fibre coupling on multiple channels, eliminating the need for beam alignment into vacuum systems and cryostats and lending robustness […]
First ever observation of ‘time crystals’ interacting
EurekAlert August 17, 2020 Protecting coherence is the main difficulty hindering the development of powerful quantum computers. An international team of researchers (Finland, UK, USA – Yale University, Russia) cooled superfluid helium-3 to within one ten thousandth of a degree from absolute zero and created two time crystals inside the superfluid. They observed an exchange of magnons between the time crystals leading to opposite-phase oscillations leading to opposite-phase oscillations in their populations while the defining periodic motion remains phase coherent throughout the experiment. The findings offer a basis to further investigate the fundamental properties of these phases, opening pathways for […]