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Category: quantum physics – Page 2

A tiny detector for microwave photons could advance quantum tech

Detecting a single particle of light is hard; detecting a single microwave photon is even harder. Microwave photons, the tiny packets of electromagnetic radiation used in current technologies like Wi-Fi and radar, carry far less energy than visible light. They are about 100,000 times weaker than optical photons.

Many existing quantum technologies depend on detecting individual photons with high reliability. For visible light, this is well established using devices that convert incoming light directly into electrical signals. But at microwave frequencies (0.3–30 GHz), this fails because each individual photon doesn’t carry enough energy to release an electric charge into a material. This means that detecting single microwave photons requires a completely different strategy.

A long-standing goal has been to realize a simple device capable of continuously detecting microwave photons. Now, scientists at EPFL, led by Pasquale Scarlino, have developed a semiconductor-based detector that takes an important step in that direction.

Small quantum system outperforms large classical networks in real-world forecasting

Can a handful of atoms outperform a much larger digital neural network on a real-world task? The answer may be yes. In a study published in Physical Review Letters, a team led by Prof. Peng Xinhua and Assoc. Prof. Li Zhaokai from the University of Science and Technology of China of the Chinese Academy of Sciences demonstrated that a quantum processor comprising just nine interacting spins outperforms classical networks with thousands of nodes in realistic weather forecasting tasks.

By exploiting unique quantum features such as superposition and entanglement, quantum devices offer new ways to represent and process information.

Recent experiments have shown their advantages in specialized benchmark tasks, but extending these gains to real-world applications remains a challenge. In particular, many quantum approaches rely on complex circuits that are difficult to implement accurately on today’s noisy hardware.

World’s largest quantum circuit simulation for quantum chemistry achieved on 1,024 GPUs

A joint research team between the Center for Quantum Information and Quantum Biology (QIQB) at The University of Osaka and Fixstars Corporation has demonstrated one of the world’s largest classical simulations of iterative quantum phase estimation (IQPE) circuits for quantum chemistry on up to 1,024 GPUs, surpassing the previous 40-qubit limit. The result expands the scale of molecular systems available for the development and validation of quantum algorithms for future fault-tolerant quantum computers, supporting progress toward industrial applications in drug discovery and materials development.

The paper was presented at NVIDIA GTC 2026, held in San Jose, California, March 16–19, 2026.

Overcoming unresolved challenges in drug discovery and developing new materials to address climate change will require advanced quantum chemical calculations beyond the reach of current technology. Against this backdrop, fault-tolerant quantum computers (FTQC) are widely anticipated as a key enabling technology, making it increasingly important to develop and validate, ahead of their deployment, the quantum algorithms that will eventually run on such systems.

Extending the Adiabatic Theorem

Jerk the support from which a swinging pendulum hangs, and you will change the pendulum’s motion. But move the support very gradually, and the system will adapt so that the pendulum’s motion relative to its support remains unchanged. A similar principle holds true for quantum systems. The quantum adiabatic theorem says that a system, when perturbed sufficiently slowly, remains in its instantaneous ground state. Sarah Damerow and Stefan Kehrein of the University of Göttingen in Germany now show that aspects of this principle remain true even for the opposite limit: The ground state remains the single most likely state even for a quantum system subjected to an instantaneous perturbation [1].

Formally, the quantum adiabatic theorem describes how a perturbed system’s Hamiltonian evolves in time. It shows that, for a slow perturbation, the system transitions from its initial ground state to the time-evolved Hamiltonian’s ground state with a probability greater than the combined probabilities of all the excited states.

Damerow and Kehrein used analytical and numerical tools to examine a quantum system undergoing rapid perturbation. They considered a quantum Ising model—a lattice of interacting magnetic spins—subjected to a rapidly changing external field. They found that the system was more likely to evolve from its initial ground state to the time-evolved Hamiltonian’s ground state than to any given excited state—provided that the lattice was in the same magnetic phase (paramagnetic or ferromagnetic) in both ground states.

Building desktop particle accelerators to unlock new realms of research

Using high-intensity lasers, researchers have taken an important step toward miniaturization of particle accelerators by demonstrating free-electron laser amplification at extreme ultraviolet wavelengths (27–50 nm), with an acceleration length of only a few millimeters. By generating high-quality, monoenergetic electron beams (i.e. beams where all the electrons have nearly the same energy), they have achieved a key milestone toward compact accelerator technologies.

The work is published in the journal Physical Review Research.

The research team led by The University of Osaka’s Institute of Scientific and Industrial Research (SANKEN) in collaboration with Kansai Institute for Photon Science (KPSI), National Institutes for Quantum Science and Technology (QST), RIKEN SPring-8 Center (RSC), High Energy Accelerator Research Organization (KEK), used a technique called laser wakefield acceleration to create plasma waves that generate extremely strong accelerating electric fields, thanks to waves within the plasma that travel at almost the speed of light.

Useful quantum computers could be built with as few as 10,000 qubits, team finds

Quantum computers of the future may be closer to reality thanks to new research from Caltech and Oratomic, a Caltech-linked start-up company. Theorists and experimentalists teamed up to develop a new approach for reducing the errors that riddle today’s rudimentary quantum computers. Whereas these machines were previously thought to require millions of qubits to work properly (qubits being the quantum equivalent to 1’s and 0’s in classical computers), the new results indicate that a fully realized quantum computer could be built with as few as 10,000 to 20,000 qubits. The need for fewer qubits means that quantum computers could, in theory, be operational by the end of the decade.

The team proposes a new quantum error-correction architecture that is significantly more efficient than previous approaches. Quantum error correction is a process by which extra, redundant qubits are introduced to correct errors, or faults, enabling the ultimate goal in the field: fault-tolerant quantum computing.

The results exploit special properties of quantum computing platforms built out of neutral atoms, which serve as the qubits. Alternative platforms in development include superconducting circuits and trapped ions (ions are charged whereas neutral atoms are not). In a neutral atom system, laser beams known as optical tweezers are used to arrange atoms into qubit arrays. Manuel Endres, a professor of physics at Caltech, and his colleagues recently created the largest qubit array ever assembled, containing 6,100 trapped neutral atoms.

Ultrafast quantum light pulses measured for the first time

Researchers at the Technion—Israel Institute of Technology have, for the first time, measured the temporal duration of individual pulses of an extraordinary form of quantum light known as bright squeezed vacuum (BSV). Their findings are published in Optica.

Bright squeezed vacuum is a unique quantum state of light. Although it is formally considered the “vacuum state” and the electric field of this light is zero on average, it exhibits enormous quantum fluctuations of its electric field due to the squeezing effect.

This is in stark contrast to typical light produced by intense lasers, known as coherent-state light, that exhibit only extremely weak quantum fluctuations. However, for BSV, the fluctuations can lead to extremely intense light pulses, containing up to one trillion (10¹²) photons in a single pulse, hence the term bright squeezed vacuum. Until now, no one had measured the temporal duration of single BSV pulses.

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