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Category: quantum physics

Paul Dirac

From that insight, Dirac built an entirely new formulation of the theory using what he called “q-numbers” (quantum numbers)—abstract quantities that don’t commute. He independently rediscovered aspects of Hilbert’s operator theory, though he preferred his own algebraic route because he found mathematicians’ obsession with convergence and existence theorems unappealing.

Paul Adrien Maurice Dirac (, dih-RAK ; [ 3 ] 8 August 1902 – 20 October 1984) was a British theoretical physicist who is considered to be one of the founders of quantum mechanics. [ 4 ] [ 5 ] Dirac laid the foundations for both quantum electrodynamics and quantum field theory, coining the former term. [ 6 ] [ 7 ] [ 8 ] [ 9 ] He was Lucasian Professor of Mathematics at the University of Cambridge from 1932 to 1969, and a professor of physics at Florida State University from 1970 to 1984. Dirac shared the 1933 Nobel Prize in Physics with Erwin Schrödinger “for the discovery of new productive forms of atomic theory.” [ 10 ]

Dirac graduated from the University of Bristol with a Bachelor of Science in Electrical Engineering in 1921, and a Bachelor of Arts in Mathematics in 1923. [ 11 ] Dirac then graduated from St John’s College, Cambridge, with a Doctor of Philosophy in Physics in 1926, writing the first ever thesis on quantum mechanics. [ 12 ]

He formulated the Dirac equation, one of the most important results in physics, in 1928. [ 7 ] It connected special relativity and quantum mechanics and predicted the existence of antimatter. [ 13 ] He wrote a famous paper in 1931, [ 14 ] which further predicted the existence of antimatter. [ 15 ] [ 16 ] [ 13 ] Dirac also contributed greatly to the reconciliation of general relativity with quantum mechanics. He contributed to Fermi–Dirac statistics, which describes the behaviour of fermions, particles with half-integer spin. His 1930 monograph, The Principles of Quantum Mechanics, is one of the most influential texts on the subject. [ 17 ] He and Schrödinger tied for eighth in a Physics World poll of the greatest physicists of all time. [ 18 ] .

Evidence of scaling advantage for the quantum approximate optimization algorithm on a classically intractable problem

We study the scaling of QAOA TTS with the problem size on the low autocorrelation binary sequences (LABS) problem (15, 16), also known as the Bernasconi model in statistical physics (17, 18). The LABS problem has applications in communications engineering, where the low autocorrelation sequences are used for designing radar pulses (15, 19). To solve LABS, one has to produce a sequence of N bits that minimizes a specific quartic objective.

We choose LABS to study the scaling of QAOA TTS for the following three reasons. First, the complexity of LABS grows rapidly, with optimal solutions known only for N ≤ 66 and the best heuristics producing approximate solutions of quality decaying with N for N 200 (20, 21). This makes it a promising candidate problem, since only a few hundred qubits are required to tackle classically intractable instances. Second, the performance of classical solvers for LABS has been benchmarked (20, 21) in terms of the scaling of their TTS with problem size. Since optimal solutions are only known for N ≤ 66, the scaling of TTS for all classical solvers is obtained by fitting results for N ≤ 66. We reproduce these results and observe that that the scaling of classical solvers at N ≤ 40 matches the behavior for N up to 66 reported in the literature. This provides evidence that the scaling we observe for QAOA at N ≤ 40 will similarly extrapolate to larger N. Third, LABS has only one instance per problem size N. Combined with the hardness of LABS, this makes it possible to reliably study the scaling of QAOA at large problem sizes, where simulating tens or hundreds of random instances would be computationally infeasible.

We obtain the scaling by performing noiseless exact simulation of QAOA with fixed schedules. Our results are enabled by a custom algorithm-specific graphics processing unit (GPU) simulator (22), which we execute using up to 1,024 GPUs per simulation on the Polaris supercomputer accessed through the Argonne Leadership Computing Facility. We find that the TTS of QAOA with number of layers p = 12 grows as 1.46N, which is improved to 1.21N if combined with quantum minimum finding. This scaling is better than that of the best classical heuristic, which has a TTS that grows as 1.34N. We note that we do not propose any new quantum algorithms in this work. Instead, we study a general quantum optimization heuristic with broad applicability (namely, QAOA) and make no specific modifications to adapt it to the LABS problem.

Quantum vibronics research points to future energy and computing technologies

Scientists at the University of California, Riverside are making breakthroughs in understanding how quantum wave functions move across ultra-thin materials—research that could eventually improve solar energy technologies and help lay the groundwork for new forms of quantum computing.

The researchers are part of UCR’s Center for Quantum Vibronics in Energy and Time (QuVET), which was established two years ago and focuses on “vibronics,” the interaction between vibrations and electronic quantum states. The center examines both biological molecules and synthetic layered materials, where the same fundamental quantum processes emerge across vastly different systems.

Its research brings together physicists, chemists, engineers, and biochemists from multiple institutions to better understand how vibrations shape quantum behavior.

Cobalt honeycombs open a new path to quantum computing

Honeycombs are famous for their elegant design, but now they may have found a new application: quantum computing. To collect knowledge from subatomic particles, quantum computers require carefully designed materials capable of performing necessary, complex functions. However, the metals used, such as ruthenium and iridium, are often rare and expensive, limiting the potential to build new technology.

In an article recently published in Physical Review Materials, researchers from SANKEN at The University of Osaka and collaborating institutions reported the creation of a special thin-film material in which cobalt atoms formed local honeycomb arrangements embedded inside a larger honeycomb matrix. These cobalt honeycomb motifs exhibit strong magnetic interactions, which are important for quantum computing applications.

Kitaev materials, a class of quantum magnetic materials studied for their potential use in quantum information science, have attracted major attention because they may host exotic quantum states known as spin liquids.

Quantum pendulum clock overcomes classical accuracy limits and sheds light on quantum to classical transitions

In a grandfather clock, a pendulum swings back and forth and this periodic motion is maintained using the energy stored in its suspended weights. This is done with the help of the escapement mechanism, which converts the gravitational energy of the weights into impulses that drive the pendulum, which then moves the clock’s gears, which move its hands.

A group of researchers recently designed a quantum version of the pendulum clock. According to their new study, published in Physical Review A, this quantum pendulum clock can operate autonomously and is more accurate than previous quantum clocks.

Quantum entanglement provides a new framework for understanding chemical bonding

Chemical bonding is one of the central organizing principles of the microscopic world. It determines how atoms combine and thereby governs a wide range of physical and chemical properties of quantum systems across many length scales, ranging from small molecules and biomolecules to macroscopically large solid materials.

Yet, despite its fundamental importance and its prominent role already in high school science education, chemical bonds remain surprisingly elusive from the perspective of quantum mechanics. They are indispensable for describing matter, even though they are not directly observable quantities.

In a recent article published in Nature Communications, the group led by LMU physicist Christian Schilling and member of the MCQST Cluster of Excellence, addresses this long-standing challenge using concepts from quantum information theory.

The generation of massive Schrödinger cat states using ultracold atoms

Quantum mechanics is a physics framework that describes how matter and energy behave at an extremely small scale, specifically at the scale of atoms and subatomic particles. An effect predicted by the laws of quantum mechanics is superposition, which entails that particles can exist in multiple states or positions simultaneously, which remain indefinite until they are measured or observed.

A well-known example of a quantum state in which a system behaves as if it is in two contrasting states at once is the so-called Schrödinger cat state. This state is rooted in a paradox introduced by physicist Erwin Schrödinger, who proposed that if a cat is placed inside a sealed box with a device that has a 50% chance of killing it, the cat is simultaneously alive and dead until someone opens the box and looks inside it.

Researchers at Southern University of Science and Technology and the Quantum Science Center of Guangdong–Hong Kong–Macao Greater Bay Area recently demonstrated the experimental generation of massive Schrödinger cat states using ultracold atoms—atoms cooled down to temperatures near to absolute zero.

Electrical ‘knob’ can switch light on, off and tune intensity at the nanoscale

Physicists from Emory University have led work to develop a microscopic, nonlinear light source that can be switched on, off or tuned to a particular intensity by an electrical “knob.” The paper is published in the journal Optica, and could aid in the design of smaller, more flexible technologies for communications, sensing and quantum computing.

The new method focuses on a type of nonlinear optics known as second harmonic generation (SHG), where two photons of the same frequency interact with a material and combine into a single photon with twice the frequency.

“Nobody had previously shown that you can tune second harmonic generation with an electric knob in such a small device,” says Hayk Harutyunyan, senior author of the paper and Emory professor of physics.

Time Itself Seems to Have a Limit of Precision Due to a Quantum Physics Model

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Hello and welcome! My name is Anton and in this video, we will talk about a proposition that time precision has a major limit.
Links:
https://journals.aps.org/prresearch/p…
Other videos: • Atomic Clock Breakthrough Could Lead To Qu…
• Most Accurate Time Keeping Device in the W…
#quantumphysics #time #science.

0:00 Limits of time measurement.
0:45 Quantum mechanics and why some things happen certain ways.
2:38 Spontaneous collapse model explained.
5:00 Gravity doesn’t like quantum stuff.
7:10 New study — effects on time measurement.
8:50 How accurate then?
10:25 Implications.
11:30 Can this be proven?
12:30 Conclusions.

Enjoy and please subscribe.

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