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Archive for the ‘quantum physics’ category: Page 9

May 29, 2019

On-demand, photonic entanglement synthesizer

Posted by in categories: engineering, quantum physics

Quantum information protocols are based on a variety of entanglement modes such as Einstein-Podolsky-Rosen (EPR), Greenberger-Horne-Zeilinger (GHZ) and other cluster states. For on-demand preparation, these states can be realized with squeezed light sources in optics, but such experiments lack versatility as they require a variety of optical circuits to individually realize diverse states of entanglement. In a recent study, Shuntaro Takeda and colleagues at the interdisciplinary departments of Applied Physics and Engineering in Japan addressed the shortcoming by developing an on-demand entanglement synthesizer. Using the experimental setup, the physicists programmably generated entangled states from a single squeezed source of light.

In the work, they used a loop-based circuit dynamically controlled at nanosecond time scales to process optical pulses in the time domain. The scientists generated and verified five different small-scale entangled states and a large-cluster containing more than 1000 modes in a single setup without changing the optical circuit. The circuit developed by Takeda et al. could store and release one part of the generated entangled states to function as a quantum memory. The experimental report published on Science Advances, will open a new way to build general entanglement synthesizers on-demand using a scalable quantum processor.

Entanglement is essential for many quantum information protocols in qubit and continuous variable (CV) regions, where they perform a variety of applications. For instance, the two-mode Einstein-Podolsky-Rosen (EPR) state is the most commonly used, maximally entangled state as a building block for two-party quantum communication and for quantum logic gates based on quantum teleportation. The generalized version of this state is an n-mode Greenberger-Horne-Zeilinger (GHZ) state central to building a quantum network, where the GHZ quantum state can be shared between n participants. For example, the n participants can communicate with each other for quantum secret sharing. For quantum computation on the other hand, a special type of entanglement known as cluster states has attracted much attention as a universal resource to allow one-way quantum computation.

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May 29, 2019

Soon ‘noise-cancelling headphones’ for quantum computers

Posted by in categories: computing, quantum physics

Quantum computers encode information in delicate superposition states of quantum bits, or ‘qubits’.

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May 29, 2019

Quantum noise and stochastic reduction

Posted by in categories: evolution, information science, law, quantum physics

Abstract: In standard nonrelativistic quantum mechanics the expectation of the energy is a conserved quantity. It is possible to extend the dynamical law associated with the evolution of a quantum state consistently to include a nonlinear stochastic component, while respecting the conservation law. According to the dynamics thus obtained, referred to as the energy-based stochastic Schrodinger equation, an arbitrary initial state collapses spontaneously to one of the energy eigenstates, thus describing the phenomenon of quantum state reduction. In this article, two such models are investigated: one that achieves state reduction in infinite time, and the other in finite time. The properties of the associated energy expectation process and the energy variance process are worked out in detail. By use of a novel application of a nonlinear filtering method, closed-form solutions—algebraic in character and involving no integration—are obtained for both these models. In each case, the solution is expressed in terms of a random variable representing the terminal energy of the system, and an independent noise process. With these solutions at hand it is possible to simulate explicitly the dynamics of the quantum states of complicated physical systems.

From: Dorje C. Brody [view email]

[v1] Mon, 29 Aug 2005 13:22:36 UTC (43 KB)

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May 29, 2019

Quantum Invisibility Cloak Hides Objects from Reality

Posted by in category: quantum physics

Physicists have worked out how to cloak a region of space from the quantum world, thereby shielding it from reality itself.

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May 28, 2019

Honeywell One Step Closer To Universal Quantum Computer

Posted by in categories: computing, quantum physics

The quantum computing effort at Honeywell appears to be heating up. Over the last several months, the company has announced a series of new developments in its trapped ion quantum computer research, which suggests that it is close to launching its first system.

If you weren’t aware that Honeywell had a quantum computing program, you are not alone. While the occasional terse news statement about this effort is posted on the company’s quantum solutions page, the tech giant has otherwise been rather tight-lipped about its plans in this area. A request from us for more information was met with: “We don’t have anything further to add on this front.”

Since October of last year, Honeywell has been offering these smaller tidbits on a regular basis. In November, the company revealed it had started testing its first-generation qubit devices, followed in January by the claim that it had “demonstrated record-breaking high fidelity quantum operations” on its trapped-ion qubits. In March, it announced it had demonstrated “parallel operating zones” on the device, which it believes will provide faster execution and more flexible qubit connectivity.

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May 28, 2019

Researchers demonstrate constraints on symmetries from holography

Posted by in categories: particle physics, quantum physics

A pair of researchers, one at the Massachusetts Institute of Technology (MIT) and another at California Institute of Technology (Caltech) and the University of Tokyo, have recently investigated a set of old conjectures about symmetries in quantum gravity. The specific conjectures of focus: Quantum gravity does not allow for global symmetries; For gauge symmetry, all possible charges must be realized; Internal gauge groups must be compact. Their paper, published in Physical Review Letters, shows that these old assumptions hold within the anti-de Sitter/conformal field theory (AdS-CFT) correspondence.

“Historically, the concept of symmetry has played important roles in physics, both in identifying and formulating fundamental laws of nature, and in using these laws to understand and predict natural phenomena such as dynamics and phases of matters,” Hirosi Ooguri, one of the researchers who carried out the study, told Phys.org. “However, there has been theoretical evidence to suggest that, once we combine and (the two fundamental ideas in modern physics), all global symmetries are gone.”

In physics, symmetries can be of two kinds: gauge and global. For several decades, researchers have proposed the idea that global symmetries should not be possible in , as the unified theory of gravity and quantum mechanics would not allow for any symmetry. This is a profound claim with important consequences. For instance, it predicts that a proton would not be stable against decaying into other particles.

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May 27, 2019

This New State of Matter Is a Liquid and a Solid at the Same Time!

Posted by in categories: particle physics, quantum physics, robotics/AI, space

Scientist have just discovered that, at an atomic level, these elements have both liquid and solid states, giving context to what may be hidden in the cores of celestial bodies.

A New State of Water Reveals a Hidden Ocean in Earth’s Mantle — https://youtu.be/pgm4z8vJVVk

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May 27, 2019

Quantum information in quantum cognition

Posted by in categories: neuroscience, particle physics, quantum physics

Some research topics, says conventional wisdom, a physics PhD student shouldn’t touch with an iron-tipped medieval lance: sinkholes in the foundations of quantum theory. Problems so hard, you’d have a snowball’s chance of achieving progress. Problems so obscure, you’d have a snowball’s chance of convincing anyone to care about progress. Whether quantum physics could influence cognition much.

Quantum physics influences cognition insofar as (i) quantum physics prevents atoms from imploding and (ii) implosion inhabits atoms from contributing to cognition. But most physicists believe that useful entanglement can’t survive in brains. Entanglement consists of correlations shareable by quantum systems and stronger than any achievable by classical systems. Useful entanglement dies quickly in hot, wet, random environments.

Brains form such environments. Imagine injecting entangled molecules A and B into someone’s brain. Water, ions, and other particles would bombard the molecules. The higher the temperature, the heavier the bombardment. The bombardiers would entangle with the molecules via electric and magnetic fields. Each molecule can share only so much entanglement. The more A entangled with the environment, the less A could remain entangled with B. A would come to share a tiny amount of entanglement with each of many particles. Such tiny amounts couldn’t accomplish much. So quantum physics seems unlikely to affect cognition significantly.

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May 26, 2019

Computer Scientists Expand the Frontier of Verifiable Knowledge

Posted by in categories: computing, quantum physics

The universe of problems that a computer can check has grown. The researchers’ secret ingredient? Quantum entanglement.

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May 26, 2019

Microsoft, Alphabet team up to teach quantum computer programming

Posted by in categories: computing, quantum physics

Microsoft, Alphabet and Brilliant are offering a course that teaches you the ins and outs of quantum computer coding.

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