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Quantum counterfeiters might succeed

Money encoded by photons should be secure, but physicists find loophole

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7:00am, March 13, 2017
quantum money

QUANTUM CASH  Physicists have created quantum money by encoding data with light. The researchers transmitted a quantum version (right) of a real bill, an old Austrian banknote (left). Each grayscale shade in the quantum bill corresponds to a different photon polarization.

Scientists have created an ultrasecure form of money using quantum mechanics — and immediately demonstrated a potential security loophole.

Under ideal conditions, quantum currency is impossible to counterfeit. But thanks to the messiness of reality, a forger with access to sophisticated equipment could skirt that quantum security if banks don’t take appropriate precautions, scientists report March 1 in npj Quantum Information. Quantum money as a concept has been around since the 1970s, but this is the first time anyone has created and counterfeited quantum cash, says study coauthor Karel Lemr, a quantum physicist at Palacký University Olomouc in the Czech Republic.

Instead of paper banknotes, the researchers’ quantum bills are minted in light. To transfer funds, a series of photons — particles of light — would be transmitted to a bank using the photons’

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