Quantum collaboration demonstrates in Chicagoland the first steps toward functional long-distance quantum networks over deployed telecom fiber optics, opening the door to scalable quantum computing — https://bit.ly/3QXe780
Category: quantum physics – Page 641
Researchers achieve record entanglement of quantum memories
A network in which data transmission is perfectly secure against hacking? If physicists have their way, this will become reality one day with the help of the quantum mechanical phenomenon known as entanglement. For entangled particles, the rule is: If you measure the state of one of the particles, then you automatically know the state of the other. It makes no difference how far away the entangled particles are from each other. This is an ideal state of affairs for transmitting information over long distances in a way that renders eavesdropping impossible.
A team led by physicists Prof. Harald Weinfurter from LMU and Prof. Christoph Becher from Saarland University have now coupled two atomic quantum memories over a 33-kilometer-long fiber optic connection. This is the longest distance so far that anyone has ever managed entanglement via a telecom fiber.
The quantum mechanical entanglement is mediated via photons emitted by the two quantum memories. A decisive step was the researchers’ shifting of the wavelength of the emitted light particles to a value that is used for conventional telecommunications. “By doing this, we were able to significantly reduce the loss of photons and create entangled quantum memories even over long distances of fiber optic cable,” says Weinfurter.
Science Breakthrough — Researchers Develop First Quantum Metamaterial
An international team consisting of Russian and German scientists has made a breakthrough in the creation of seemingly impossible materials. They have managed to create the world‘s first quantum metamaterial which can be used as a control element in superconducting electrical circuits.
Metamaterials.
Metamaterials are engineered materials that have properties not usually found in nature.
Physicists Record Temporal Coherence of a Graphene Qubit
Recently, researchers have been incorporating graphene-based materials into superconducting quantum computing devices, which promise faster, more efficient computing, among other perks. Until now, however, there’s been no recorded coherence for these advanced qubits, so there’s no knowing if they’re feasible for practical quantum computing.
In a paper published today in Nature Nanotechnology, the researchers demonstrate, for the first time, a coherent qubit made from graphene and exotic materials. These materials enable the qubit to change states through voltage, much like transistors in today’s traditional computer chips — and unlike most other types of superconducting qubits. Moreover, the researchers put a number to that coherence, clocking it at 55 nanoseconds, before the qubit returns to its ground state.
The work combined expertise from co-authors William D. Oliver, a physics professor of the practice and Lincoln Laboratory Fellow whose work focuses on quantum computing systems, and Pablo Jarillo-Herrero, the Cecil and Ida Green Professor of Physics at MIT who researches innovations in graphene.
Scientists invent ‘quantum flute’ that can make particles of light move together
University of Chicago physicists have invented a “quantum flute” that, like the Pied Piper, can coerce particles of light to move together in a way that’s never been seen before.
Described in two studies published in Physical Review Letters and Nature Physics, the breakthrough could point the way towards realizing quantum memories or new forms of error correction in quantum computers, and observing quantum phenomena that cannot be seen in nature.
Assoc. Prof. David Schuster’s lab works on quantum bits —the quantum equivalent of a computer bit—which tap the strange properties of particles at the atomic and sub-atomic level to do things that are otherwise impossible. In this experiment, they were working with particles of light, known as photons, in the microwave spectrum.
The Spooky Quantum Phenomenon You’ve Never Heard Of
But Cabello and others are interested in investigating a lesser-known but equally magical aspect of quantum mechanics: contextuality. Contextuality says that properties of particles, such as their position or polarization, exist only within the context of a measurement. Instead of thinking of particles’ properties as having fixed values, consider them more like words in language, whose meanings can change depending on the context: “Time flies like an arrow. Fruit flies like bananas.”
Although contextuality has lived in nonlocality’s shadow for over 50 years, quantum physicists now consider it more of a hallmark feature of quantum systems than nonlocality is. A single particle, for instance, is a quantum system “in which you cannot even think about nonlocality,” since the particle is only in one location, said Bárbara Amaral, a physicist at the University of São Paulo in Brazil. “So [contextuality] is more general in some sense, and I think this is important to really understand the power of quantum systems and to go deeper into why quantum theory is the way it is.”
Researchers have also found tantalizing links between contextuality and problems that quantum computers can efficiently solve that ordinary computers cannot; investigating these links could help guide researchers in developing new quantum computing approaches and algorithms.
Novel quantum simulation method clarifies correlated properties of complex material 1T —TaS2
A team led by Philipp Werner, professor of physics at the University of Fribourg and leader of NCCR MARVEL’s Phase 3 project Continued Support, Advanced Simulation Methods, has applied their advanced quantum simulation method to the investigation of the complex material 1T-TaS2. The research, recently published in Physical Review Letters, helped resolve a conflict between earlier experimental and theoretical results, showing that the surface region of 1T-TaS2 exhibits a nontrivial interplay between band insulating and Mott insulating behavior when the material is cooled to below 180 k.
1T-TaS2 is a layered transition metal dichalcogenide that has been studied intensively for decades because of intriguing links between temperature dependent distortions in the lattice and phenomena linked to electronic correlations.
Upon cooling, the material undergoes a series of lattice rearrangements with a simultaneous redistribution of the electronic density, a phenomenon known as charge density wave (CDW) order. In the phase reached when the material is cooled to below 180 k, an in-plane periodic lattice distortion leads to the formation of star-of-David (SOD) clusters made of 13 tantalum atoms. Simultaneously, a strong increase in resistivity is observed. Additional interesting properties of the low temperature phase include a transition to a superconducting state under pressure as well as the possibility to switch this phase into long-lived metallic metastable phases by applying short pulses of laser or voltage, making the material potentially interesting for use in future memory devices.
Mathematical calculations show that quantum communication across interstellar space should be possible
A team of physicists at the University of Edinburgh’s School of Physics and Astronomy has used mathematical calculations to show that quantum communications across interstellar space should be possible. In their paper published in the journal Physical Review D, the group describes their calculations and also the possibility of extraterrestrial beings attempting to communicate with us using such signaling.
Over the past several years, scientists have been investigating the possibility of using quantum communications as a highly secure form of message transmission. Prior research has shown that it would be nearly impossible to intercept such messages without detection. In this new effort, the researchers wondered if similar types of communications might be possible across interstellar space. To find out, they used math that describes that movement of X-rays across a medium, such as those that travel between the stars. More specifically, they looked to see if their calculations could show the degree of decoherence that might occur during such a journey.
With quantum communications, engineers are faced with quantum particles that lose some or all of their unique characteristics as they interact with obstructions in their path—they have been found to be quite delicate, in fact. Such events are known as decoherence, and engineers working to build quantum networks have been devising ways to overcome the problem. Prior research has shown that the space between the stars is pretty clean. But is it clean enough for quantum communications? The math shows that it is. Space is so clean, in fact, that X-ray photons could travel hundreds of thousands of light years without becoming subject to decoherence—and that includes gravitational interference from astrophysical bodies. They noted in their work that optical and microwave bands would work equally well.