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Category: quantum physics – Page 627

A new type of quasiparticle

Russian scientists have experimentally proved the existence of a new type of quasiparticle—previously unknown excitations of coupled pairs of photons in qubit chains. This discovery could be a step towards disorder-robust quantum metamaterials. The study was published in Physical Review B.

Superconducting qubits are a leading qubit modality today that is currently being pursued by industry and academia for quantum computing applications. However, the performance of quantum computers is largely affected by decoherence that contributes to a qubit’s extremely short lifespan and causes computational errors. Another major challenge is low controllability of large qubit arrays.

Metamaterial quantum simulators provide an alternative approach to quantum computing, as they do not require a large amount of control electronics. The idea behind this approach is to create artificial matter out of qubits, the physics of which will obey the same equations as for some real matter. Conversely, you can program the simulator in such a way as to embody matter with properties that have not yet been discovered in nature.

Quantum-computing startup Rigetti to offer modular processors

A quantum-computing startup announced Tuesday that its future quantum processor designs will differ significantly from its current offerings. Rather than building a monolithic processor as everyone else has, Rigetti Computing will build smaller collections of qubits on chips that can be physically linked together into a single functional processor. This isn’t multiprocessing so much as modular chip design.

The move is consequential for both Rigetti processors and quantum computing more generally.

Is Reality a Game of Quantum Mirrors?

Imagine you sit down and pick up your favourite book. You look at the image on the front cover, run your fingers across the smooth book sleeve, and smell that familiar book smell as you flick through the pages. To you, the book is made up of a range of sensory appearances.

But you also expect the book has its own independent existence behind those appearances. So when you put the book down on the coffee table and walk into the kitchen, or leave your house to go to work, you expect the book still looks, feels, and smells just as it did when you were holding it.

Expecting objects to have their own independent existence – independent of us, and any other objects – is actually a deep-seated assumption we make about the world. This assumption has its origin in the scientific revolution of the 17th century, and is part of what we call the mechanistic worldview. According to this view, the world is like a giant clockwork machine whose parts are governed by set laws of motion.

The quantum world of diamonds

3 mins. This is really fascinating. Several applications, including quantum computing. Need special diamonds that scientists now can produce.

Diamonds are dazzling physicists with their powerful quantum properties. A particular impurity — the nitrogen-vacancy (NV) centre — allows diamonds to be used for everything from geolocation to diagnosing disease. This animation takes a closer look at these NV centres, and the carefully crafted artificial diamonds that make them possible.

Quantum Birds: Breakthrough Discovery on Mechanism of Magnetic Sensing in Birds

Humans perceive the world around them with five senses — vision, hearing, taste, smell and touch. Many other animals are also able to sense the Earth’s magnetic field. For some time, a collaboration of biologists, chemists and physicists centred at the Universities of Oldenburg (Germany) and Oxford (UK) have been gathering evidence suggesting that the magnetic sense of migratory birds such as European robins is based on a specific light-sensitive protein in the eye. In the current edition of the journal Nature, this team demonstrate that the protein cryptochrome 4, found in birds’ retinas, is sensitive to magnetic fields and could well be the long-sought magnetic sensor.

First author Jingjing Xu, a doctoral student in Henrik Mouritsen’s research group in Oldenburg, took a decisive step toward this success. After extracting the genetic code for the potentially magnetically sensitive cryptochrome 4 in night-migratory European robins, she was able, for the first time, to produce this photoactive molecule in large quantities using bacterial cell cultures. Christiane Timmel’s and Stuart Mackenzie’s groups in Oxford then used a wide range of magnetic resonance and novel optical spectroscopy techniques to study the protein and demonstrate its pronounced sensitivity to magnetic fields.

The team also deciphered the mechanism by which this sensitivity arises — another important advance. “Electrons that can move within the molecule after blue-light activation play a crucial role,” explains Mouritsen. Proteins like cryptochrome consist of chains of amino acids: robin cryptochrome 4 has 527 of them. Oxford’s Peter Hore and Oldenburg physicist Ilia Solov’yov performed quantum mechanical calculations supporting the idea that four of the 527 — known as tryptophans — are essential for the magnetic properties of the molecule. According to their calculations, electrons hop from one tryptophan to the next generating so-called radical pairs which are magnetically sensitive. To prove this experimentally, the team from Oldenburg produced slightly modified versions of the robin cryptochrome, in which each of the tryptophans in turn was replaced by a different amino acid to block the movement of electrons.

In Extraordinary Experiment, Physicists Bring Human-Scale Object to Near Standstill, Reaching a Quantum State

The results open possibilities for studying gravity’s effects on relatively large objects in quantum states.

To the human eye, most stationary objects appear to be just that — still, and completely at rest. Yet if we were handed a quantum lens, allowing us to see objects at the scale of individual atoms, what was an apple sitting idly on our desk would appear as a teeming collection of vibrating particles, very much in motion.

In the last few decades, physicists have found ways to super-cool objects so that their atoms are at a near standstill, or in their “motional ground state.” To date, physicists have wrestled small objects such as clouds of millions of atoms, or nanogram-scale objects, into such pure quantum states.

Achieving Precision in Quantum Material Simulations

In fall of 2019, we demonstrated that the Sycamore quantum processor could outperform the most powerful classical computers when applied to a tailor-made problem. The next challenge is to extend this result to solve practical problems in materials science, chemistry and physics. But going beyond the capabilities of classical computers for these problems is challenging and will require new insights to achieve state-of-the-art accuracy. Generally, the difficulty in performing quantum simulations of such physical problems is rooted in the wave nature of quantum particles, where deviations in the initial setup, interference from the environment, or small errors in the calculations can lead to large deviations in the computational result.

In two upcoming publications, we outline a blueprint for achieving record levels of precision for the task of simulating quantum materials. In the first work, we consider one-dimensional systems, like thin wires, and demonstrate how to accurately compute electronic properties, such as current and conductance. In the second work, we show how to map the Fermi-Hubbard model, which describes interacting electrons, to a quantum processor in order to simulate important physical properties. These works take a significant step towards realizing our long-term goal of simulating more complex systems with practical applications, like batteries and pharmaceuticals.

MIT Makes a Significant Advance Toward the Full Realization of Quantum Computation

MIT researchers demonstrate a way to sharply reduce errors in two-qubit gates, a significant advance toward fully realizing quantum computation.

MIT researchers have made a significant advance on the road toward the full realization of quantum computation, demonstrating a technique that eliminates common errors in the most essential operation of quantum algorithms, the two-qubit operation or “gate.”

“Despite tremendous progress toward being able to perform computations with low error rates with superconducting quantum bits (qubits), errors in two-qubit gates, one of the building blocks of quantum computation, persist,” says Youngkyu Sung, an MIT graduate student in electrical engineering and computer science who is the lead author of a paper on this topic published on June 16, 2021, in Physical Review X. “We have demonstrated a way to sharply reduce those errors.”

Rare Superconductor Discovered – May Be Critical for the Future of Quantum Computing

Research led by Kent and the STFC Rutherford Appleton Laboratory has resulted in the discovery of a new rare topological superconductor, LaPt3P. This discovery may be of huge importance to the future operations of quantum computers.

Superconductors are vital materials able to conduct electricity without any resistance when cooled below a certain temperature, making them highly desirable in a society needing to reduce its energy consumption.

They manifest quantum properties on the scale of everyday objects, making them highly attractive candidates for building computers that use quantum physics to store data and perform computing operations, and can vastly outperform even the best supercomputers in certain tasks. As a result, there is an increasing demand from leading tech companies like Google, IBM and Microsoft to make quantum computers on an industrial scale using superconductors.