Researchers are diligently working towards making quantum computers a reality but there are many hurdles for them to overcome. One of these is finding a way to transfer information from a piece of matter to a photon. While particles, in this case ions, work well for storing information, photons, the quanta of light, are the preferred media for transmitting information, because they travel at the speed of light. Researchers at the University of Innsbruck have developed a new means to create an entangled photon ion pair which may help bring quantum computers and quantum networking to the present.
The researchers' new device holds a calcium ion in a Paul trap, which is placed between two mirrors. A laser is then aimed at the ion, to excite it enough to emit a photon of its own. Properties of this photon are entangled with properties of the ion, because the ion emitted it and left its fingerprint, as it were. The photon then bounces off the two mirrors about 25,000 times, causing it to interact with the ion many more times, and become more entangled, until it finally escapes into an optical fiber.
Other devices have been made that will entangle an ion and a photon but this new device surpasses them as it offers very high precision and efficiency. By carefully tuning the frequency and amplitude of the laser that stimulates the ion, the researchers can tune the entanglement between the ion and photon to whatever they wish. Also, while the probability of successful entanglement for this specific device was not given, the researchers are confident a similar device could achieve an efficiency of over 99%.