This issue, as I understand it, is quantum decoherence, when quantum properties are lost as an object transitions into the behavior of classical physics.
The article describes a period of a millisecond before quantum decoherence occurs. This is (relatively) a long time, and perhaps could be exploited in part to build a quantum computer.
The article is saying this can be avoided in their system for a _microsecond_, still long enough to be potentially useful.
> The hologram cascade is synthesized by solving an inverse problem with respect to the propagation of incoherent light.
From "Learning quantum Hamiltonians at any temperature in polynomial time" (2024) https://arxiv.org/abs/2310.02243 .. https://www.hackerneue.com/item?id=40396171 :
>> The relaxation technique is well known in the field of approximation algorithms, but it had never been tried in quantum learning.
Relaxation (iterative method) https://en.wikipedia.org/wiki/Relaxation_(iterative_method)
Pertubation theory > History > Beginnings in the study of planetary motion ... QFT > History: https://en.wikipedia.org/wiki/Perturbation_theory#Beginnings...
QFT > History: https://en.wikipedia.org/wiki/Quantum_field_theory#History :
> Quantum field theory emerged from the work of generations of theoretical physicists spanning much of the 20th century. Its development began in the 1920s with the description of interactions between light and electrons, culminating in the first quantum field theory—quantum electrodynamics. A major theoretical obstacle soon followed with the appearance and persistence of various infinities in perturbative calculations, a problem only resolved in the 1950s with the invention of the renormalization procedure. A second major barrier came with QFT's apparent inability to describe the weak and strong interactions, to the point where some theorists called for the abandonment of the field theoretic approach. The development of gauge theory and the completion of the Standard Model in the 1970s led to a renaissance of quantum field theory.
But the Standard Model Lagrangian doesn't describe n-body gravity, n-body quantum gravity, photons in Bose-Einstein Condensates; liquid light in superfluids and superconductors, black hole thermodynamics and external or internal topology, unreversibility or not, or even fluids with vortices or curl that certainly affect particles interacting in multiple fields.
TIL again about Relaxation theory for solving quantum Hamiltonians.
OTOH other things on this topic
- "Coherent interaction of a-few-electron quantum dot with a terahertz optical resonator" (2023) https://arxiv.org/abs/2204.10522 :
> By illuminating the system with THz radiation [a wave function (Hamiltonian) is coherently transmitted over a small chip-scale distance]
- "Room Temperature Optically Detected Magnetic Resonance of Single Spins in GaN" (2024) https://www.nature.com/articles/s41563-024-01803-5 ... "GAN semiconductor defects could boost quantum technology" https://www.hackerneue.com/item?id=39365467
- "Reversible non-volatile electronic switching in a near-room-temperature van der Waals ferromagnet" (2024) https://www.nature.com/articles/s41467-024-46862-z ... "Nonvolatile quantum memory: Discovery points path to flash-like qubit storage" (2024) https://www.hackerneue.com/item?id=39956368 :
>> "That's the key finding," she said of the material's switchable vacancy order. "The idea of using vacancy order to control topology is the important thing. That just hasn't really been explored. People have generally only been looking at materials from a fully stoichiometric perspective, meaning everything's occupied with a fixed set of symmetries that lead to one kind of electronic topology. Changes in vacancy order change the lattice symmetry. This work shows how that can change the electronic topology. And it seems likely that vacancy order could be used to induce topological changes in other materials as well."
- "Catalog of topological phonon materials" (2024) https://www.science.org/doi/10.1126/science.adf8458 ... "Topological Phonons Discovered and Catalogued in Crystal Lattices" (2024-05) https://www.hackerneue.com/item?id=40410475
- "Observation of current whirlpools in graphene at room temperature" (2024) https://www.science.org/doi/10.1126/science.adj2167 .. "Electron Vortices in Graphene Detected" https://www.hackerneue.com/item?id=40360691 :
> re: the fractional quantum hall effect, and decoherence: How are spin currents and vorticity in electron vortices related?
- If you mean excited states of the neutrons and protons in the nucleus, I really have no idea, mainly because these are generally unachievable in an engineered system. These excitations are in the gamma-ray spectrum and just way too high-energy and destructive to be useful, so no one has tried to harness them for quantum information processing.
- If you mean the "orientation" of the spin of the nucleus, which can be easily manipulated with reasonably weak low-frequency magnetic fields (like we already do classically for medical imagining purposes), then this is actually a pretty good storage medium. Frequently people think of the electron spin as the "networking card" because it can easily interface with photonic qubits, and think of the nuclear spin as the storage medium because nuclear spins can retain quantum information for many minutes (because they are so well isolated). One problem is that transferring the data from the electron spin to the nuclear spin is relatively slow and noisy. But "progress is being made" albeit less quickly than we would like.
My claim to authority here is that I have designed various control protocols for such hardware during my postdoctoral time. But I had it easy, most of my work includes statements roughly equivalent to "assuming the progress of the last 20 years continues, we will have good qubits in 10 years if we use the protocol suggested here". To be clear, there are technologies that will be workable sooner (or already are), they just have different tradeoffs in cost and other requirements.
- Usually the problem with room temperature is that the various thermal mechanical excitation and thermal radiation surrounding the qubit lead to interaction with the qubit and the information stored in it "leaks"; that is the main reason a lot of quantum hardware needs cryogenics.
- There are already a couple of similar types of "defects" that are known as a promising way to retain superposition states at room temperature. They work because the defect happens to be mechanically and/or optically isolated from the rest of the environment due to some idiosyncrasies in its physical composition.
- You might have heard of "trapped ion" or "trapped neutral atom" quantum hardware. In those the qubits are atoms (or the electrons of atoms) and they are trapped (with optical or RF tweezers) so they are kept accessible. The type of "defects" discussed here are "simply" atoms trapped in a crystal lattice instead of trapped in optical tweezers -- there are various tradeoffs for that choice.
- While discoveries like this are extremely exciting, there is a completely separate set of issues about scalability, reliability, longevity, controlability, and reproducible fabrication of devices like this. That is true for any quantum hardware and while there are great improvements over the last 15 years and while there is truly exponential progress over that time, we are still below the threshold of this technology being engineeringly and economically useful.
Lastly, the usual reminder: there are a few problems in computing, communication, and sensing, where quantum devices can do things that are impossible classically, but these are very restricted and niche problems. For most things a classical device is not only practically better today, but also is in-principle better even if quantum computers become trivial to build.