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Category: quantum physics – Page 382

For the first time, physicists have observed novel quantum effects in a topological insulator at room temperature. This breakthrough, published as the cover article of the October issue of Nature Materials, came when Princeton scientists explored a topological material based on the element bismuth.

The scientists have used topological insulators to demonstrate for more than a decade, but this experiment is the first time these effects have been observed at room temperature. Typically, inducing and observing quantum states in topological insulators requires temperatures around absolute zero, which is equal to-459 degrees Fahrenheit (or-273 degrees Celsius).

This finding opens up a new range of possibilities for the development of efficient quantum technologies, such as spin-based electronics, which may potentially replace many current electronic systems for higher energy efficiency.

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In February 2019, JQI Fellow Alicia Kollár, who is also an assistant professor of physics at UMD, bumped into Adrian Chapman, then a postdoctoral fellow at the University of Sydney, at a quantum information conference. Although the two came from very different scientific backgrounds, they quickly discovered that their research had a surprising commonality. They both shared an interest in graph theory, a field of math that deals with points and the connections between them.

Chapman found graphs through his work in —a field that deals with protecting fragile quantum information from errors in an effort to build ever-larger quantum computers. He was looking for new ways to approach a long-standing search for the Holy Grail of quantum error correction: a way of encoding quantum information that is resistant to errors by construction and doesn’t require active correction. Kollár had been pursuing new work in graph theory to describe her photon-on-a-chip experiments, but some of her results turned out to be the missing piece in Chapman’s puzzle.

Their ensuing collaboration resulted in a new tool that aids in the search for new quantum error correction schemes—including the Holy Grail of self-correcting quantum error correction. They published their findings recently in the journal Physical Review X Quantum.

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Light-pulse matter-wave interferometers exploit the quantized momentum kick given to atoms during absorption and emission of light to split atomic wave packets so that they traverse distinct spatial paths at the same time. Additional momentum kicks then return the atoms to the same point in space to interfere the two matter-wave wave packets. The key to the precision of these devices is the encoding of information in the phase ϕ that appears in the superposition of the two quantum trajectories within the interferometer. This phase must be estimated from quantum measurements to extract the desired information. For N atoms, the phase estimation is fundamentally limited by the independent quantum collapse of each atom to an r.m.s. angular uncertainty \(\Delta {\theta }_{{\rm{SQL}}}=1/\sqrt{N}\) rad, known as the standard quantum limit (SQL)2.

Here we demonstrate a matter-wave interferometer31,32 with a directly observed interferometric phase noise below the SQL, a result that combines two of the most striking features of quantum mechanics: the concept that a particle can appear to be in two places at once and entanglement between distinct particles. This work is also a harbinger of future quantum many-body simulations with cavities26,27,28,29 that will explore beyond mean-field physics by directly modifying and probing quantum fluctuations or in which the quantum measurement process induces a phase transition30.

Quantum entanglement between the atoms allows the atoms to conspire together to reduce their total quantum noise relative to their total signal1,3. Such entanglement has been generated between atoms using direct collisional33,34,35,36,37,38,39 or Coulomb40,41 interactions, including relative atom number squeezing between matter waves in spatially separated traps33,35,39 and mapping of internal entanglement onto the relative atom number in different momentum states42. A trapped matter-wave interferometer with relative number squeezing was realized in ref. 35, but the interferometer’s phase was antisqueezed and thus the phase resolution was above the SQL.

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Physicists have created the first Bose-Einstein condensate—the mysterious fifth state of matter—made from quasiparticles, entities that do not count as elementary particles but that can still have elementary-particle properties like charge and spin. For decades, it was unknown whether they could undergo Bose-Einstein condensation in the same way as real particles, and it now appears that they can. The finding is set to have a significant impact on the development of quantum technologies including quantum computing.

A paper describing the process of creation of the substance, achieved at temperatures a hair’s breadth from absolute zero, was published in the journal Nature Communications.

Bose-Einstein condensates are sometimes described as the fifth state of matter, alongside solids, liquids, gases and plasmas. Theoretically predicted in the early 20th century, Bose-Einstein condensates, or BECs, were only created in a lab as recently as 1995. They are also perhaps the oddest state of matter, with a great deal about them remaining unknown to science.

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Basically the fibonacci sequence stabilized the quantum computers internal processes better essentially. This may fall into the theory of everything that supersymmetry and the fibonacci sequence can get us closer to a theory of everything even in quantum computers.

A dynamical topological phase with edge qubits that are dynamically protected from control errors, cross-talk and stray fields, is demonstrated in a quasiperiodically driven array of ten 171Yb+ hyperfine qubits in a model trapped-ion quantum processor.

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