How to Draw a Quantum Bath . . .

[Recusant]

I considered "Not Tonight, I Have to Take a Quantum Bath" and a few others even less notable, but went with a more descriptive flippancy.

"Finally! After 20 Years, Major Quantum Entanglement Theory Has Been Experimentally Confirmed" | ScienceAlert

Quantum mechanics is so odd that even the visionary genius who described the secrets of the Universe seemed to dismiss certain aspects as eerie.

"Spooky action at a distance" is how Albert Einstein described quantum entanglement, a weird connection between particles that classical physics cannot explain.

From our classical perspective, it seems to allow instantaneous communication, thereby breaking the speed of light and garnering Einstein's ire.

For example, if we flipped two quantum-entangled coins and one landed heads up, we could know for sure whether the second coin would instantly land tails up – even if one were flipped on Earth and the other on Mars.

That's because measuring one instantly reveals the state of the other, a correlation with no classical explanation.

This spooky synchronization is a basis for quantum computing, with untold potential for machine learning, pharmaceutical design, digital communications, and other essential applications.

Now, physicists at the Institute of Science and Technology Austria (ISTA) and the Technical University of Munich in Germany have achieved a breakthrough by experimentally confirming a 20-year-old entanglement theory, providing a prototype for scaling up quantum computing processes.

Not too dissimilar from hosing down an irascible chihuahua, the researchers used a 'quantum bath' of light particles to entangle isolated qubits (quantum bits), the functional units of quantum computers.

[. . .]

This quantum bath method offers a fully autonomous way to synchronize distant qubits by subjecting them both to low-energy microwaves, yielding a "stationary," applicable version of entanglement, rather than one that fluctuates in its properties like a pendulum.

"In this work, we aimed to overcome this mismatch between the readily available and the practically useful forms of entanglement," explains Alejandro Andrés-Juanes, a physicist at ISTA and the study's first author.

"By stabilizing the entangled states remotely, our approach is fully autonomous and requires no active control or measurement."

Importantly, this scheme can be applied over "arbitrary distances," ostensibly farther than the 50 centimeters (20 inches) of cable that separated the qubits from the entanglement-inducing photons in this experiment.

Additionally, a single correlated (entangled) photon source can be manipulated to generate many entangled pairs.

[ Continues . . .]

The paper is open access.

"Distributing Stationary Qubit Entanglement through a Nonlocal Squeezed Reservoir" | Physical Review X

Abstract:

The distribution of entanglement across distant qubits is a central challenge for the operation of scalable quantum computers and large-scale quantum networks. Existing approaches rely on deterministic state transfer, or probabilistic protocols that require active control or measurements and postselection.

Here, we demonstrate a fundamentally different, fully autonomous process, where two remote qubits are entangled through their coupling to a quantum-correlated photonic reservoir. In our experiment, a Josephson parametric converter produces a Gaussian, continuous-variable entangled state of propagating microwave fields that drives two spatially separated superconducting transmon qubits into a stationary, discrete-variable entangled state.

We also show how qubit tomography unlocks a direct and sensitive verification of two-mode squeezing in the microwave domain. These results establish networks of qubits interfaced with distributed continuous-variable entangled states as a powerful platform for foundational studies and quantum-technology applications.