Physics World October 10, 2019 A team of researchers in the US (University of Rochester, Purdue University) has demonstrated coherent spin-state transfer along an array of four electrons confined in a quadruple quantum dot in a GaAs/AlGaAs heterostructure. When they applied a voltage pulse to a gate between two quantum dots, the electrons in the dots exchanged their spin states via Heisenberg exchange coupling. By applying a series of voltage pulses to specific gates, the researchers were able to shuttle the spin states of the electrons back and forth. They were able to transmit the spins of entangled electrons using […]
Tag Archives: Quantum computers
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 […]
Physicists can predict the jumps of Schrodinger’s cat (and finally save it)
Phys.org June 3, 2019 An international team of researchers (USA – Yale University, New Zealand) used a special approach to indirectly monitor a superconducting artificial atom, with three microwave generators irradiating the atom enclosed in a 3-D cavity made of aluminum. Microwave radiation stirs the artificial atom as it is simultaneously being observed, resulting in quantum jumps. They amplified the tiny quantum signal of these jumps and monitored it in real time which enabled the researchers to see a sudden absence of detection photons which was a warning of a quantum jump. Despite its observation, coherence increased during the jump. […]
Computing faster with quasi-particles
Eurekalert May 10, 2019 Majorana particles can emerge as quasi-particles in topological superconductors and represent ideal building blocks for topological quantum computers. Whereas previous experiments in this field have mostly focused on one-dimensional systems an international team of researchers (USA – Harvard University, Caltech, IBM Watson Research Laboratory, Germany) succeeded in going to two-dimensional systems. They observed a topological phase transition in their proof of concept system which implies the appearance of Majorana fermions in phase-controlled Josephson junctions confirming the advantages of two-dimensional system compared to previous one-dimensional platforms. An improved control of Majorana fermions represents an important step towards […]
Quantum bugs, meet your new swatter
Science Daily August 20, 2018 According to a team of researchers in the US (Rice University, University of Maryland, industry, UT Austin) when a quantum computer executes an algorithm, it starts at a specific state. The state at the very end is the answer to the algorithm’s question. Reassembling the full state from these measurements, one can later pinpoint hardware or software errors that may have caused the computer to deliver unexpected results. However, the computational cost of reconstruction can be high even as few as five or six qubits. The team solved the validation problem with an algorithm they […]
Physicists Just Broke a Quantum Record, Taking Entanglement to a Spooky New Level
Science Alert April 16, 2018 An international team of researchers (Austria, Germany) used an ion trap to confine calcium ions using a magnetic field. They used lasers to entangle the ions, creating a 20-qubit system, with each qubit encoded into the electronic state of a trapped atomic ion. Their quantum states can be individually controlled, and they were able to individually read and address each of the qubits. The team were able to get the calcium ions to entangle with two, three, or occasionally even four other calcium ions in the system… read more. Open Access TECHNICAL ARTICLE
Quantum shift shows itself in coupled light and matter
Science Daily April 16, 2018 An international team of researchers (USA – Rice University, Argonne National Laboratory, Purdue University, Japan) created resonance frequency shift in solid gallium arsenide in a strong perpendicular magnetic field. They hybridize with the “vacuum” electromagnetic field in the cavity to form polaritons. They have demonstrated Bloch–Siegert shift, which is induced by the ultra-strong coupling of matter with the counter-rotating component of the vacuum fluctuation field in a cavity. The research could aid in the development of quantum computers… read more. Open Access TECHNICAL ARTICLE
New quantum spin liquid predicted by Nobel Laureate prepared for the first time
Eurekalert March 15, 2018 In 1987 Paul W. Anderson, a Nobel Prize winner in Physics, proposed that high-temperature superconductivity is related to quantum spin liquid. An international team of researchers (Finland, Brazil, Germany, Switzerland, UK, Japan) has developed a new way of tailoring the properties of magnetic materials to produce the superconductor-like quantum spin liquid predicted by Anderson. This achievement is an important step towards building topological quantum computers… read more. Open Access TECHNICAL ARTICLE
What’s the noise eating quantum bits?
Phys.org January 8, 2018 The ability to develop SQUID-based quantum computers will require the stored magnetic data survive for long times. Theory calculations by a team of researchers in the US (University of Wisconsin–Madison, Argonne National Laboratory, UC Irvine, NIST-Colorado), showed that adsorbed molecular oxygen on the surfaces is the dominant contributor to magnetic noise for superconducting niobium and aluminum thin films. They found that surface treatment with ammonia and improving the sample vacuum environment dramatically reduced the surface contamination (to less than one oxygen molecule per 10 nm2), minimizing magnetic noise. Their work provides a design strategy for the […]
Quantum simulators wield control over more than 50 qubits, setting new record
Source: Science Daily, November 29, 2017 Two independent teams of researchers in the US (University of Maryland, NIST) and (Harvard University, MIT) have used more than 50 interacting atomic qubits to mimic magnetic quantum matter. UMD-NIST team deployed ytterbium ions trapped in place by gold-coated and razor-sharp electrodes and Harvard-MIT team used rubidium atoms confined by an array of laser beams. In this experiment there are over a quadrillion possible magnet configurations, and this number doubles with each additional magnet. Quantum simulations are believed to be one of the first useful applications of quantum computers. After perfecting these quantum simulators, […]