See David Kaiser's account of the Chickering letter in "How the Hippies Saved Physics" before the mainstream physics community even had a clue about this.
Submarines must be able to talk securely with remote naval bases while remaining submerged. Could quantum communications allow them to pull off this technically challenging feat?
Submarines employ random "keys" known as one-time pads to encrypt messages. Each key can only be used once, making it impossible for eavesdroppers to crack the code.
One problem with this is that the key must be securely agreed before the submarine leaves base. There is a risk involved in having many keys on board, in case the sub is captured and they fall into hostile hands.
The other problem is that submarines receive messages using low-frequency radio waves that can penetrate water, but only a few characters per second can be transmitted at these frequencies. To receive high frequencies, which can boost the data rate, submarines have to surface and risk detection.
"You want the submarine to be undetectable for as long as possible - we're talking about several weeks," says Marco Lanzagorta, director of quantum technologies at US defence firm ITT.
He suggests that a technique called quantum key distribution (QKD) could solve these problems. It uses the quantum properties of photons, which are polarised in two different ways to encode 0s and 1s, to generate and exchange a key. Any attempt to intercept the photons disturbs these properties and raises the alarm.
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