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The new experiment demonstrated a bizarre quantum effect from the double-slit experiment at an unprecedented scale.
Category: quantum physics – Page 617
To understand the behavior of quantum particles, imagine a pinball game—but rather than one metal ball, there are billions or more, all ricocheting off each other and their surroundings.
Physicists have long tried to study this interactive system of strongly correlated particles, which could help illuminate elusive physics phenomena like high-temperature superconductivity and magnetism.
One classic method is to create a simplified model that can capture the essence of these particle interactions. In 1963, physicists Martin Gutzwiller, Junjiro Kanamori and John Hubbard—working separately—proposed what came to be called the Hubbard model, which describes the essential physics of many interacting quantum particles. The solution to the model, however, only exists in one dimension. For decades, physicists have tried to realize the Hubbard model in two or three dimensions by creating quantum simulators that can mimic it.
I think these can be fought with current technology such as quantum radar even other higher level technology. It can also be hacked with quantum radar or neutrino beams.
Know colloquially as the “Black Holes” by the U.S. Navy, the Improved-Kilo-class of submarines are quite deadly — and could turn the balance of power in the South China Sea in China’s favor.
Clause density is something new to me but seems interesting as I know shores algorithm is the only thing that can hack systems.
Google is racing to develop quantum-enhanced processors that utilize quantum mechanical effects to one day dramatically increase the speed at which data can be processed.
In the near term, Google has devised new quantum-enhanced algorithms that operate in the presence of realistic noise. The so-called quantum approximate optimization algorithm, or QAOA for short, is the cornerstone of a modern drive towards noise-tolerant quantum-enhanced algorithm development.
The celebrated approach taken by Google in QAOA has sparked vast commercial interest and ignited a global research community to explore novel applications. Yet, little actually remains known about the ultimate performance limitations of Google’s QAOA algorithm.
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The quantum spin Hall insulator is characterized by a bandgap in the two-dimensional (2D) interior and helical 1D edge states1,2,3. Inducing superconductivity in the helical edge state results in a 1D topological superconductor, a highly sought-after state of matter at the core of many proposals for topological quantum computing4. In the present study, we report the coexistence of superconductivity and the quantum spin Hall edge state in a van der Waals heterostructure, by placing a monolayer of 1T′-WTe2, a quantum spin Hall insulator1,2,3, on a van der Waals superconductor, NbSe2. Using scanning tunnelling microscopy and spectroscopy (STM/STS), we demonstrate that the WTe2 monolayer exhibits a proximity-induced superconducting gap due to the underlying superconductor and that the spectroscopic features of the quantum spin Hall edge state remain intact. Taken together, these observations provide conclusive evidence for proximity-induced superconductivity in the quantum spin Hall edge state in WTe2, a crucial step towards realizing 1D topological superconductivity and Majorana bound states in this van der Waals material platform.
The race toward the first practical quantum computer is in full stride. Companies, countries, collaborators, and competitors worldwide are vying for quantum supremacy. Google says it’s already there. But what does that mean? How will the world know when it’s been achieved?
Using classical computers, computational scientists at PNNL have set a mark that a quantum system would need to surpass to establish quantum supremacy in the realm of chemistry.
That’s because the fastest classical computers available today are getting better and better at simulating what a quantum computer will eventually be expected to do. To prove itself in the real world, a quantum computer will need to be able to outdo what a fast supercomputer can do. And that’s where the PNNL-led team have set a benchmark for quantum computers to beat.
Can we realize non-trivial condensed-matter phases – such as topological insulating phases – in the time dimension? Topological insulators are condensed-matter systems that are insulators in their interior but, by virtue of the topological properties of the electronic structure, have conducting surface (edge) states. They are characterized by global topological invariants. An example of a topological invariant is the number of holes a surface has: a sphere has no holes while a torus has one. It is hard to change such a topological invariant because it is not possible to gradually introduce a hole in a sphere in order to change it to a torus – either there is a hole or there is no hole, but there is nothing like a fraction of a hole. Even the vacuum (empty space) has trivial topological invariants. In order to reconcile a change of this invariant at the interface between the vacuum and a topological insulator, there are surface (edge) states that close the gap between the energy bands of the insulator, thereby producing conducting behaviour.
Can a quantum swing behave like an electron in a topological insulator? Yes, for example if we ask the child to push with a combination of a resonant frequency ω and a sub-harmonic frequency ω /2 (Optica 5 1390, New J. Phys. 21 052003). Then the motion of the swing effectively creates a chain of lattice sites along the resonant orbit with staggered hopping amplitudes, and thus reproduces an example of a topological system, called the Su–Schrieffer–Heeger lattice. In order to observe the edge states, we need to create an “edge” in the motion of the swing and then check if there are quantum states that are localized close to it. How can we create an edge in time? We ask the child to jump on the swing from time to time, which introduces a barrier in the chain of lattice sites along the resonant orbit and consequently breaks the time-translational symmetry along the orbit, similar to how a surface breaks spatial-translational symmetry in an ordinary topological insulator.
Simulating computationally complex many-body problems on a quantum simulator has great potential to deliver insights into physical, chemical and biological systems. Physicists had previously implemented Hamiltonian dynamics but the problem of initiating quantum simulators to a suitable quantum state remains unsolved. In a new report on Science Advances, Meghana Raghunandan and a research team at the institute for theoretical physics, QUEST institute and the Institute for quantum optics in Germany demonstrated a new approach. While the initialization protocol developed in the work was largely independent of the physical realization of the simulation device, the team provided an example of implementing a trapped ion quantum simulator.
Quantum simulation is an emergent technology aimed at solving important open problems relative to high-temperature superconductivity, interacting quantum field theories or many-body localization. A series of experiments have already demonstrated the successful implementation of Hamiltonian dynamics within a quantum simulator—however, the approach can become challenging across quantum phase transitions. In the new strategy, Raghunandan et al. overcame this problem by building on recent advances in the use of dissipative quantum systems to engineer interesting many-body states.
Almost all many-body Hamiltonians of interest remain outside a previously investigated class and therefore require generalization of the dissipative state preparation procedure. The research team therefore presented a previously unexplored paradigm for the dissipative initialization of a quantum simulator by coupling the many-body system performing the quantum simulation to a dissipatively driven auxiliary particle. They chose the energy splitting within the auxiliary particle to become resonant with the many-body excitation gap of the system of interest; described as the difference of the ground-state energy and the energy of the first excited state. During such conditions of resonance, the energy of the quantum simulator could be transferred efficiently to the auxiliary particle for the former to be cooled sympathetically, i.e., particles of one type, cooled particles of another type.
Our current, well-established understanding of phases of matter primarily relates to systems that are at or near thermal equilibrium. However, there is a rich world of systems that are not in a state of equilibrium, which could host new and fascinating phases of matter.
Recently, studies focusing on systems outside of thermal equilibrium have led to the discovery of new phases in periodically driven quantum systems, the most well-known of which is the discrete time crystal (DTC) phase. This unique phase is characterized by collective subharmonic oscillations arising from the interplay between many-body interactions and non-equilibrium driving, which leads to a loss of ergodicity.
Interestingly, subharmonic oscillations are also known to be a characteristic of dynamical systems, such as predator-prey models and parametric resonances. Some researchers have thus been exploring the possibility that these classical systems may exhibit similar features to those observed in the DTC phase.