photonic qubit tagged posts

Researchers demonstrate the first single-photon transistor using a semiconductor chip. They used a single photon, stored in a quantum memory, to toggle the state of other photons. Credit: E. Edwards/Joint Quantum Institute

Researchers have demonstrated the first single-photon transistor using a semiconductor chip. Transistors are tiny switches that form the bedrock of modern computing; billions of them route electrical signals around inside a smartphone, for instance. Quantum computers will need analogous hardware to manipulate quantum information. But the design constraints for this new technology are stringent, and today’s most advanced processors can’t be repurposed as quantum devices. That’s because qubits, have to follow different rules laid out by quantum physics.

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A cloud of cold atoms is illuminated with red signal light and blue coupling light. The light pulses are superimposed on dichroic mirrors (DM). With wave plates (WP), a polarizing beam splitter (PBS), and avalanche photodiodes (APD) the polarization of the transmitted signal light is determined. Credit: MPQ, Quantum Dynamics Division

MPQ scientists take an important step towards a logical quantum gate for photons. Commonly, a typical quantum computer is considered to be based on a network of quantum particles that serve for storing, encoding and processing quantum information. In analogy to the case of a classical computer a quantum logic gate that assigns output signals to input signals in a deterministic way would be an essential building block...