Phys.org October 1, 2024 A team of researchers in the US (University of Michigan, DEVCOM Army Research Laboratory) investigated the possible realization of an ultracold-atom rotation sensor that was based on recently proposed tractor atom interferometry (TAI). They described an experimental design that included the generation of a Laguerre–Gaussian-beam-based “pinwheel” optical lattice and multi-loop interferometric cycles. Numerical simulations of the proposed system demonstrated TAI rotation sensitivity comparable to that of contemporary matter-wave interferometers. They applied quantum optimal control to devise a methodology suitable to address nonadiabaticity which might hinder systems performance. According to the researchers their studies are of interest […]
Category Archives: Quantum science
Quantum researchers cause controlled ‘wobble’ in the nucleus of a single atom
Phys.org September 12, 2024 The nuclear spin presents opportunities for quantum experiments with prolonged coherence times. Electron spin resonance (ESR) combined with scanning tunnelling microscopy (STM) provides a bottom-up platform to study the fundamental properties of nuclear spins of single atoms on a surface. However, access to the time evolution of nuclear spins remained a challenge. An international team of researchers (The Netherlands, Germany) developed an experiment resolving the nanosecond coherent dynamics of a hyperfine-driven flip-flop interaction between the spin of an individual nucleus and that of an orbiting electron. They used the unique local controllability of the magnetic field […]
Theoretical research holds promise for advancing modular quantum information processing
Phys.org August 15, 2024 As quantum information processing systems are scaled to many qubits to reach their full potential, highly complex electronics are needed to control the complex circuitry. A team of researchers in the US (University of Rhode Island, University of Maryland, NIST, UCLA) considered a pair of quantum dot-based spin qubits that interact via microwave photons in a superconducting cavity and parametrically driven by separate external electric fields. For this system, they formulated a model for spin qubit entanglement in the presence of mutually off-resonant qubit and cavity frequencies. They showed that the sidebands generated via the driving […]
Study unveils limits on the extent to which quantum errors can be ‘undone’ in large systems
Phys.org August 11, 2024 Recently quantum error mitigation has been successfully applied to reduce noise in near-term applications. However, an international team of researchers (Germany, USA – Harvard University, France) identified strong limitations to the degree to which quantum noise can be effectively ‘undone’ for larger system sizes. They developed a framework which rigorously captures large classes of error-mitigation schemes in use today. By relating error mitigation to a statistical inference problem, they showed that even at shallow circuit depths comparable to those of current experiments, a superpolynomial number of samples was needed in the worst case to estimate the […]
New method achieves tenfold increase in quantum coherence time via destructive interference of correlated noise
Phys.org July 10, 2024 Decoherence and imperfect control are crucial challenges for quantum technologies. Common protection strategies rely on noise temporal autocorrelation, which is not optimal if other correlations are present. An international team of researchers (Israel, Germany, USA – Caltech, industry) developed and experimentally demonstrated a strategy that used the cross-correlation of two noise sources. Utilizing destructive interference of cross-correlated noise extended the coherence time tenfold, improved control fidelity, and surpassed the state-of-the-art sensitivity for high frequency quantum sensing, significantly expanding the applicability of noise protection strategies… read more. Open Access TECHNICAL ARTICLE
Novel 2D device for quantum cooling converts heat to voltage at ultra-low temperatures
Phys.org July 5, 2024 Nernst effect has potential for energy conversion achieving high performance and versatility at low temperatures. However, achieving high performance and versatility at low temperatures remains elusive. An international team of researchers (Switzerland, Japan) demonstrated a large and electrically tunable Nernst effect by combining the electrical properties of graphene with the semiconducting characteristics of indium selenide in a field-effect geometry. Photovoltage measurements revealed a stronger photo-Nernst signal in the graphene/indium selenide heterostructure compared with individual components. They observed a record-high Nernst coefficient at ultralow temperatures and low magnetic fields, an important step towards applications in quantum information […]
An alternative way to manipulate quantum states
EurekAlert July 2, 2024 Control over quantum systems is typically achieved by time-dependent electric or magnetic fields. Alternatively, electronic spins can be controlled by spin-polarized currents. Researchers in Switzerland demonstrated coherent driving of a single spin by a radiofrequency spin-polarized current injected from the tip of a scanning tunneling microscope into an organic molecule. With the excitation of electron paramagnetic resonance, they established dynamic control of single spins by spin torque using a local electric current. Their work highlighted the dissipative action of the spin-transfer torque, in contrast to the nondissipative action of the magnetic field, which allowed for the […]
Understanding quantum states: New research shows importance of precise topography in solid neon qubits
Phys.org June 26, 2024 Single electrons trapped on solid-neon surfaces, which have long coherence times, are promising platform for charge qubits. The actual quantum states of the trapped electrons have not been understood. A team of researchers in the USA (National High Magnetic Field Laboratory (Florida), Florida State University, University of Florida, FAMU-FSU College of Engineering) examined the electron’s interactions with neon surface topography and by evaluating the surface charges induced by the electron, they demonstrated its strong perpendicular binding to the neon surface. They revealed that surface bumps could bind an electron, forming unique quantum ring states that aligned […]
Quantum entangled photons react to Earth’s spin
Phys.org June 14, 2024 Optical quantum interferometers are of particular interest because of mature methods for generating and manipulating quantum states of light. Their increased sensitivity promises to enable tests of quantum phenomena. However, this requires long and decoherence-free processing of quantum entanglement, which, for large interferometric areas, remains unexplored territory. Researchers in Austria developed a table-top experiment using maximally path-entangled quantum states of light in a large-scale interferometer sensitive enough to measure the rotation rate of Earth with high sensitivity. According to the researchers further improvements to their methodology will enable tests for fundamental physics allowing the exploration of […]
Scientists demonstrate the survival of quantum coherence in a chemical reaction involving ultracold molecules
Phys.org May 16, 2024 Chemical reactions, where bonds break and form, are highly dynamic quantum processes. A fundamental question is whether coherence can be preserved in chemical reactions and then harnessed to generate entangled products. Researchers at Harvard University investigated this by studying the 2KRb → K2 + Rb2 reaction at 500 nK, focusing on the nuclear spin degrees of freedom. They prepared the initial nuclear spins in KRb in an entangled state by lowering the magnetic field to where the spin-spin interaction dominated and characterized the preserved coherence in nuclear spin wavefunction after the reaction. They observed an interference […]