GoKawiilFuture quantum computers may depend on the ability to connect widely separated modules through distributed entanglement. Until now, creating this kind of connection has generally required active control and repeated measurements. Physicists at the Institute of Science and Technology Austria (ISTA) have now demonstrated a fully autonomous alternative based on a "quantum bath" made from correlated particles of light.
Published in Physical Review X, the experiment provides the first demonstration of a prediction proposed more than 20 years ago. The approach could eventually offer a new foundation for practical quantum technologies.
Connecting Distant Quantum Bits
Entanglement is one of the defining phenomena of quantum physics. It allows particles or systems to share correlations that cannot be explained by classical physics. Creating distributed entanglement between physically separated qubits (quantum bits) could be important for building larger quantum computers and future quantum networks.
Previous attempts to entangle distant qubits have generally followed one of two strategies. One method sends a single, actively controlled photon from one qubit to another. Another has each qubit emit a photon, with the two photons then matched in an effort to generate entanglement.
The second approach was recognized by the 2022 Nobel Prize in Physics. However, it still depends on repeated measurements and post-selection, and even then, the process does not always successfully produce entanglement.
PhD student Alejandro Andrés-Juanes and professor Johannes Fink at the Institute of Science and Technology Austria (ISTA) worked with international collaborators to develop a different solution. Their system uses a quantum bath that automatically brings distant qubits into synchronization. In a prototype device, the researchers used a shared source of correlated light particles to entangle two separated qubits, experimentally realizing an idea that had remained theoretical for more than two decades.
Fully Autonomous Quantum Entanglement
Quantum entanglement can take several forms. Continuous-variable entangled states can be produced efficiently and are therefore relatively accessible. They can be compared with a pendulum, whose position and momentum change continuously.
Many useful quantum technologies, however, depend on "discrete-variable" systems. These involve 'all-or-nothing' forms of entanglement that stationary qubits can use. The challenge for the ISTA team was finding a way to connect these readily available continuous forms of entanglement with the discrete forms needed for practical applications.
... continue reading