Single-photon all-phototransistors come out

In the latest issue of Science magazine, scientists at the Massachusetts Institute of Technology (MIT) Electronic Research Laboratory (RLE), Harvard University, and the Vienna University of Technology in Vienna wrote that it has developed a single photon-controlled system. Optical switches, new all-optical transistors are expected to benefit both traditional computers and quantum computers.

At the heart of the new all-optical switch is a pair of highly reflective mirrors. When the switch is turned on, light signals can pass through both mirrors. When the switch is off, about 20% of the light in the signal can pass through the mirror. As a result, the pair of mirrors constitute so-called optical resonators. The research leader and MIT professor of physics, Flada Ulletti, explained that if the distance between the mirrors is accurately adjusted according to the wavelength of light, then for some wavelengths of light, the mirror is transparent. Is the default "on" state.

In the ERL experiment, the cavity between the two mirrors was filled with supercooled Helium atoms. Under normal circumstances, helium atoms and light through the mirror "well water does not violate river water." However, if a “photon” enters the middle of two mirrors at different angles and pushes one electron of one atom into a higher energy state, it will change the physical properties of the cavity so that light cannot pass through the cavity. Switch off.

With the increasing number of transistors clustered on traditional computer chips, and the increasing energy consumption of chips, the all-optical transistors may solve these two problems. Of course, the ultra-cooled atomic cloud is not an ideal design for transistors in network servers. Ulletti said: "For classical calculations, this is just a conceptual experiment. We can also use impure atoms in the optical fiber or solid piece to make the same equipment."

This device may be more beneficial to quantum computers. Quantum computing relies on the inherent uncertainty of the quantum mechanism to process information, and its information processing speed is much faster than traditional machines. Ordinary information bits can only represent 0 or 1, while qubits exist in a superposition of 0 and 1. This ambiguity allows several qubits to be processed in parallel, so multiple operations can be performed at once.

Scientists have used laser trapped ions and nuclear magnetic resonance to create the original quantum computer, but it is difficult to keep the qubits superimposed, and photons are more likely to remain superimposed, allowing scientists to create a series of optical circuits in superposition. . More importantly, Ulletti said that traditional transistors can filter out noise in electrical signals, and quantum feedback can counteract quantum noise. Therefore, one can create quantum states that cannot be obtained by other methods.

This switch can also be used as a light detector that is not yet available: if photons hit the atom, light cannot pass through the cavity, which means that the device can detect its trace without destroying photons.

Stanford University's professor of electrical engineering, Jelena Ukkives, said: "The energy consumption of computing devices is a big problem. The beauty of the new device is that it can really switch in the single-photon state, so the energy loss Smaller. It should be possible to repeat the experiment on physical systems that are easier to integrate into a computer chip."