Researchers Quantum Teleport Data Across 100 Channels at Once

Quantum networks could protect messages with theoretically hack-proof encryption, as well as help quantum devices operate in unison to boost their capabilities. For the most part, scientists have sought to upgrade these networks by increasing the distance or fidelity of their communications. Now researchers in China have a new way to dramatically scale up the bandwidth of quantum networks by increasing the number of simultaneous quantum communication channels.

Quantum networks share data that encodes the key details, or quantum states, of particles.This kind of communication could connect quantum computers to allow them to behave as more powerful processors, or link quantum sensors together in arrays for even greater precision.

However, the data encoding quantum states is fragile and easily lost over great enough lengths of fiber optics. One way to overcome this problem is using quantum teleportation, in which the data essentially disappears one place and reappears someplace else. Because the information does not travel across the intervening space, there is no chance it will get lost.

Scaling Quantum Teleportation Channels

Quantum teleportation relies on quantum entanglement to connect, for example, two photons, so that they can influence each other instantly no matter how far apart they are. Then, one of the two photons would stay in one location while the other photon would be moved to whatever destination is desired.

Next, a third photon is prepared for teleportation. This third photon is entangled with the first photon and then both are analyzed, which destroys their quantum states. That data is sent to the destination, typically using light pulses, where it can be used on the other photon to recreate the teleported photon, so that it is indistinguishable from the original. (Because the data is sent using signals such as light pulses, quantum teleportation can proceed no faster than the speed of light.)

Conventional quantum teleportation sends quantum states one at a time. This makes it challenging to transfer complex information, such as images. A large quantum network “requires many quantum channels to be generated, matched, and manipulated at the same time,” says Jietai Jing, a professor of physics at East China Normal University in Shanghai.

Previous attempts to transmit multiple quantum states in parallel usually depended on multiplexing techniques that encoded multiple channels in a single beam of light. However, such techniques require decoding schemes that make it difficult to manipulate each channel independently.

The researchers in China instead devised a way to greatly expand the bandwidth of quantum networks. “We have scaled quantum teleportation up to 100 channels,” Jing says. “This architecture may contribute to high-capacity quantum communication.” They detailed their findings on 20 August in Physical Review Letters.

The new technique encodes a programmable, reconfigurable computer-generated hologram onto a device known as a spatial light modulator. The modulator passes a laser beam through this hologram in the form of a 10-by-10 grid pattern of distinct spatial modes that function as pixels. The modulator can control each spatial mode independently so they can each carry their own stream of data.

Separately, the sender and receiver share a pair of entangled light fields that constitute all of the light rays traveling in all directions. The sender entangles its light field with the hologram’s light field and transmits the resulting signal. The receiver combines this message with its entangled light field to enable quantum teleportation of all the original data at once.

In experiments, the researchers teleported a 100-pixel image of the letter Q. The new technique can support many channels simultaneously without requiring a complex set of devices to handle each channel, Jing notes. He adds that the team is now working to achieve a 1,000-channel system by using higher-power lasers and better amplifiers.