Quantum computers encode information in delicate superposition states of quantum bits, or ‘qubits’.
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Category: quantum physics – Page 664
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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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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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 gravity and quantum mechanics (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 quantum gravity, 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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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
On the chain-melted phase of matter
https://www.pnas.org/content/116/21/10297
“We develop here a classical interatomic forcefield for the element potassium using machine-learning techniques and simulate the chain-melted state with up to 20,000 atoms. We show that in the chain-melted state, guest-atom correlations are lost in three dimensions, providing the entropy necessary for its thermodynamic stability.”
Elements can be solid and liquid at same time
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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