(PhysicsWorld) The year 2020 saw some remarkable advances in quantum science and technology. Here are a few of the highlights from subfields ranging from quantum fundamentals to quantum computing.

The most precise thermometer possible
How precise can a thermometer be? In January, Jukka Pekkola, Bayan Karimi and colleagues at the University of Aalto, Finland, and Lund University in Sweden found the answer by building a nanoscale device that can detect fundamental fluctuations in the electron temperature of a sample.

Entanglement in “hot and messy” conditions
In June, physicists at the ICFO in Barcelona, Spain used a technique called a quantum non-demolition measurement to show that at least 1.52 × 1013 out of the 5.32 × 1013 rubidium atoms in their 450 K sample were, in fact, entangled. The team, led by Morgan Mitchell and Jia Kong, also showed that this entanglement was non-local, meaning that it involved atoms that were not close to each other. As well as challenging assumptions about what entanglement looks like, the finding could be important for sensing technologies such as vapour-phase spin-exchange-relaxation-free (SERF) magnetometers that are based on hot, dense clouds of atoms.

The first quantum phase battery
In June, physicists at the NEST-CNR Nanoscience Institute in Pisa and the University of Salerno, Italy demonstrated the first quantum phase battery: a device that provides a persistent phase bias to the wavefunction of a quantum circuit, similar to the way that a conventional battery provides a persistent voltage bias to an electrical circuit.

Measuring quantum tunnelling time
In July, physicists led by Aephraim Steinberg of the University of Toronto, Canada, found that ultracold rubidium-87 atoms spent 0.62 ms tunnelling through a barrier 10 000 times wider than their diameter. Their experiment sheds much-needed light on a phenomenon that remains poorly understood despite lying at the heart of practical technologies such as scanning tunnelling microscopes and flash memories.

Quantum advantage in an optical circuit
Late in 2020, the quest for “quantum advantage” hit the headlines again as researchers led by Jian-Wei Pan and Chao-Yang Lu at the University of Science and Technology of China in Hefei announced that they had performed a quantum computation called Gaussian boson sampling 100 trillion times faster than a supercomputer could.

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