Theoretically predicted quantum battery constructed
Sounds like "Star Trek", but has now been constructed: the quantum phase battery. It is designed to manipulate qubits in superconducting quantum computers.
In June, experts from Spain and Italy presented a component that had previously only been predicted in theory - and could potentially be crucial for future quantum computers. It generates a permanent phase difference between two points in a superconducting circuit, in much the same way as a conventional battery generates a voltage in a normal circuit. The quantum phase battery could play a similar role for certain quantum technologies, just as a classical circuit only does things when a voltage is applied.
A team led by Francesco Giazotto from the National Enterprise for nanoScience and nanoTechnology (NEST) in Pisa has now realised the technology that was theoretically predicted back in 2014. As the team reports in "Nature Nanotechnology", the battery consists of a nanowire made of the semiconductor indium arsenide (InAs), which is connected to superconducting contacts. The resulting change in the wave function is based on the anomalous Josephson effect. Spins and magnetic fields act on the superconducting current and generate the phase shift.
Quantum gate as the next step
For quantum technologies based on phase coherence, such a controlled phase shift is a crucial element. Not least for quantum computers with superconducting circuits. Their information carriers, the qubits, can not only be switched individually into different states using such phase differences, but can also be combined to form quantum gates, as two physicists demonstrated as early as 2010
These quantum gates correspond to the logic gates of classical computers. They generate output signals from input signals according to certain rules and thus perform basic logical operations. Without this capability, there would be no computer. However, other applications for such technologies are also being considered, for example, superconducting circuits should enable highly sensitive magnetic field measurements. Giazotto's team now wants to improve the component so that the phase shift can be specifically adjusted and the battery can be easily integrated into circuits.
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