Replies to post #9207 on SCIENCE SPIN-OFFS

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Essential for so-called quantum networks and quantum computers is something called a quantum bit, or qubit, which would replace the traditional bits that are stored or transmitted in today’s computers and optical networks. It consists of an ion with an unpaired electron that has two spin states—up or down, or a 0 and 1 in a binary system. But under some conditions, these qubits can be made to have both the 0 and 1 state simultaneously—a quantum state.

Where the researchers diverted from the norm with these photonic crystals was intentionally leaving a region of the grid pattern undrilled. This created a defect in the crystal that acted like a cavity, or a hole, in which only those photons with a certain kind of energy—in this case, infrared photons—could enter or leave.


They then embedded a quantum dot into that cavity. Quantum dots behave like artificial atoms. So, in this case, the researchers used quantum dots with a single electron orbiting it, not unlike an ion.

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Once the matched photons and quantum dots begin to interact, the spin of the electron modifies the polarization of the photon. A magnetic field is applied to the quantum dot to change the spin of the electron to either up or down. Then a technique called optical pumping is used to cool the spin so that it points along the magnetic field direction. In this way, it is possible to control the orientation of the spin using fast optical pulses.


Holy Smokes!