Lifeboat Foundation

One of the most basic assumptions of fundamental physics is that the different properties of mass—weight, inertia and gravitation—always remain the same in relation to each other. Without this equivalence, Einstein’s theory of relativity would be contradicted and our current physics textbooks would have to be rewritten. Although all measurements to date confirm the equivalence principle, quantum theory postulates that there should be a violation.

This inconsistency between Einstein’s gravitational theory and modern quantum theory is the reason why ever more precise tests of the equivalence principle are particularly important. A team from the Center of Applied Space Technology and Microgravity (ZARM) at University of Bremen, in collaboration with the Institute of Geodesy (IfE) at Leibniz University Hannover, has now succeeded in proving with 100 times greater accuracy that passive gravitational mass and active gravitational mass are always equivalent—regardless of the particular composition of the respective masses.

The research was conducted within the framework of the Cluster of Excellence “QuantumFrontiers.” Today, the team published their findings as a highlights article in Physical Review Letters.

Quantum computing holds the potential to tackle complex issues in fields like material science and cryptography, problems that will remain out of reach even for the most powerful conventional supercomputers in the future. However, accomplishing this feat will likely necessitate millions of high-quality qubits, given the error correction needed.

Progress in superconducting processors advances quickly with a current qubit count in the few hundreds. The appeal of this technology lies in its swift computational speed and compatibility with microchip fabrication. However, the requirement for extremely low temperatures places a limit on the processor’s size and prevents any physical access once it is cooled down.

A modular quantum computer with multiple separately cooled processor nodes could solve this. However, single microwave photons—the particles of light that are the native information carriers between superconducting qubits within the processors—are not suitable to be sent through a room temperature environment between the processors. The world at room temperature is bustling with heat, which easily disturbs the microwave photons and their fragile quantum properties like entanglement.

An unusual superconducting state observed in the material uranium ditelluride (UTe2) could help overcome well-known challenges in the advancement of quantum computing.

Researchers from the Macroscopic Quantum Matter Group laboratory at University College Cork (UCC) discovered the unique properties, which allow electrons to flow freely without resistance along a kind of quantum waterslide.

Envision a realm where light can be meticulously controlled and manipulated at minuscule scales, unlocking unprecedented potentials for nanotechnology and quantum information technology. Recent breakthroughs in quantum research have propelled us closer to a reality that may be more achievable than previously realized.

In this article, we delve into the domain of surface plasmon polaritons (SPPs) and the vast possibilities they offer in revolutionizing the field of quantum optics.

Picture a serene lake on a sunny day. As you drop a small stone into the water, it sets in motion gentle ripples that traverse the surface. Now, imagine light as akin to those undulating ripples. When light encounters the interface of a metal and a dielectric material, it has the power to generate waves, much like the ripples on the lake. This phenomenon is even more intriguing because these light waves can interact with the metal’s microscopic constituents, such as electrons. Remarkably, the light waves and electrons synchronize their oscillations, giving rise to an SPP wave.

What good is a powerful computer if you can’t read its output? Or readily reprogram it to do different jobs? People who design quantum computers face these challenges, and a new device may make them easier to solve.

The device, introduced by a team of scientists at the National Institute of Standards and Technology (NIST), includes two superconducting quantum bits, or qubits, which are a quantum computer’s analog to the logic bits in a classical computer’s processing chip. The heart of this new strategy relies on a “toggle switch” device that connects the qubits to a circuit called a “readout resonator” that can read the output of the qubits’ calculations.

This toggle switch can be flipped into different states to adjust the strength of the connections between the qubits and the readout resonator. When toggled off, all three elements are isolated from each other. When the switch is toggled on to connect the two qubits, they can interact and perform calculations. Once the calculations are complete, the toggle switch can connect either of the qubits and the readout resonator to retrieve the results.

The images shed light on how electrons form superconducting pairs that glide through materials without friction.

When your laptop or smartphone heats up, it’s due to energy that’s lost in translation. The same goes for power lines that transmit electricity between cities. In fact, around 10 percent of the generated energy is lost in the transmission of electricity. That’s because the electrons that carry electric charge do so as free agents, bumping and grazing against other electrons as they move collectively through power cords and transmission lines. All this jostling generates friction, and, ultimately, heat.

But when electrons pair up, they can rise above the fray and glide through a material without friction. This “superconducting” behavior occurs in a range of materials, though at ultracold temperatures. If these materials can be made to superconduct closer to room temperature, they could pave the way for zero-loss devices, such as heat-free laptops and phones, and ultra-efficient power lines. But first, scientists will have to understand how electrons pair up in the first place.

Nematicity was recently found in the kagome superconductor CsV3Sb5. Here, by performing elastoresistance measurements on Ti-doped CsV3Sb5, the authors find that nematic fluctuations play an important role in enhancing superconductivity in this material.

Pump-probe spectroscopy is a versatile technique to explore ultrafast dynamics on the femtosecond timescale. Here the authors report a pump-probe experiment and quantum modeling combined study revealing dynamics of collective polaritonic states that are formed between a molecular photoswitch and plasmonic nanoantennas.

“A phonon represents the collective motion of an astronomical number of atoms,” Cleland says. “And they all have to work together in order to obey quantum mechanics. There was this question in the back of my mind, will this really work? We tried it, and it’s kind of amazing, but it really does work.”

Splitting a phonon

The team created single phonons as propagating wavepackets on the surface of a lithium niobate chip. The phonons were created and detected using two superconducting qubits, which were located on a separate chip, and coupled to the lithium niobate chip through the air. The two superconducting qubits were located either of the chip, with a two-millimetre-long channel between them hosting the travelling phonons.