11 April 2018: Breaking Quantum Records

When the US and Russia are backing up their twitter feud over Syria with actual missiles, and the head of the International Monetary Fund describes the outlook for global trade with the words “Dark” and “Clouds”, clearly this is a day to fold up the newspaper and leave it on the park bench for someone else to angst over.

Instead, here’s a cheery news story from the science desk:

A team of physicists in Germany and Austria have set a new record for quantum entanglement, using a laser ion trap to create a system of twenty caesium atoms in a single, entangled quantum state. The result brings the tantalising promise of novel technologies such as quantum computing closer to reality.

The previous entanglement record, held since 2011 by members of the same research team, was 14 atoms. The new record required innovative experimental and theoretical advances, and the researchers are confident they can set much higher quantum records in the future.

The research group, led by Ben Lanyon and Rainer Blatt at the Institute of Quantum Optics and Quantum Information of the Austrian Academy of Sciences, with colleagues from the University of Ulm and the Institute of Quantum Optics and Quantum Information in Vienna, published their record-breaking results in Physical Review X this week.

Quantum entanglement is a mysterious but critical concept in the very modern technologies of quantum information and quantum computing. Particles in an entangled state lose their individuality; instead, their behaviour can only be described as a whole system, even when the entangled particles are separated by very large distances.

The idea goes back more than eighty years to a famous paper by Einstein, Podolsky and Rosen, and was a subject of theoretical debate for decades. In recent years, with advances in both theory and experimental ability to trap and control atoms, quantum entanglement has become a very hot field.

Entanglement leads to strange and often counter-intuitive applications, such as quantum teleportation, where information can be instantly sent from one location to another, and quantum computing, which uses entangled quantum bits, or qubits, to solve problems beyond the capability of a conventional computer.

These applications are constrained by the difficulty in producing and measuring quantum effects in systems larger than just a few atoms. Intrusions from the surrounding environment, such as heat, quickly wipes out the connections between the entangled particles, a process known as quantum decoherence.

The great challenge physicists face is creating systems with a sufficient number of entangled particles or atoms, and maintaining the systems for sufficiently long periods of time. Using laser light to trap and control twenty caesium atoms, Lanyon and Blatt’s team were able to entangle pairs of atoms, and then use novel theoretical and experimental methods to detect the spread of entanglement effects across the remainder of the system.

They have set an ambitious goal of producing an entanglement of fifty atoms. A fifty-quit quantum computer would allow physicists to solve certain classes of problems that would cause the most powerful supercomputers on the planet to choke.

Original Source: https://www.alphagalileo.org/en-gb/Item-Display/ItemId/162049

Research paper: https://journals.aps.org/prx/abstract/10.1103/PhysRevX.8.021012