Pushing quantum money can be stored in an ultra -cold ‘debit card’

A rudimentary quantum card has been made that can be loaded with unforgettable quantum money, of extremely cold atoms and party roses of light.

In ordinary banks depends on discovering a counterfeit banknotes often on the forgery, but in a Quantum Bank a physics law called the non-cloning sentence would make a successful counterfeit impossible. This law says identical copies of quantum information simply cannot be made, and in 1983 devised physicist Stephen Wiesner a protocol that utilizes the theorem without cloning to create unforgettable currency. Julien Laurat at Kastler Brossel Laboratory in France and his colleagues have now implied the idea of ​​the most advanced experiment.

In this protocol is a bank from banknotes made of quantum particles that have a special set of properties-a specific quantum state and are protected from the forgery of the non-cloning theorem. Laurat says that the protocol itself is a usual work in quantum crryptography, but it has never been implified in such a way that the user could store quantum money – the fragility of quantum states means that a use would have to emulate it.

His team has made such storage possible by integrating memory devices similar to hard drives into their setup. In their experiment, the user communicates with a quantum interior that plays the bank’s role by exchanging light particles or photons. The state of each photon can be deposited in memory, analogous to loading a debit card.

The team’s memory unit was made by several chased millions of cesium atoms, which scientists cooled to just a few million of a degree over absolutely zero by hitting them with lasers. At this extreme temperature, the atoms’ quantum booths could be controlled very precisely with light, but Laurat says it took yers to decide how to do well enough for the cold atomic memory to act as a quantum. Through repeated tests, he and his colleagues showed photons can be taken effectively from the atoms when the user wants to use their quantum money without the states of corrupt in the process.

Christoph Simon at the University of Calgary in Canada says the new experiment is a step towards full quantum money, but the storage time of the quantum memory, which is approx. 6 million dollars of a second is still too short for the protocol to be convenient. “Another [future step] is to include portability. I think the long -term goal, especially in the quantum money context, would be a quantum memory that you can put in your pocket. But we are not defined there yet, ”he says.

The team has their signs of increasing this storage time – if we have a thousand times line, the protocol could be used within Metropolitan Quantworks that already exist in cities around the world, says Laurat. In addition, advanced quantum memories could enable ultra -safe long -term quantum communication as well as helping connecting more quantum computers to one, more powerful device, he says.