Quantum information is still a relatively young area of interdisciplinary research. One of its main goals is to combine the principles of quantum physics and information theory. Apart from its conceptual importance, quantum information may lead to real-world applications for communication (“quantum communication”) and computation (“quantum computation”) by exploiting quantum properties such as the superposition principle and entanglement. Quantum optics is a more traditional field in which light is described via quantum theory, leading to, for instance, optical modes in superposition states of different photon numbers.
The optical quantum information theory group conducts research on systems and protocols for processing quantum information, primarily by optical means using photonic quantum states composed of either a few or many photons. More specifically, this includes protocols for processing quantum information on a small scale and for communicating quantum information on a large scale, with current or near-future, optical technology, and with an emphasis on measurement-based quantum computation, long-distance quantum communication via quantum repeaters, quantum error correction, and linear-optics schemes.
In an optical hybrid approach to quantum information processing and communication, both discrete and continuous degrees of freedom are to be utilized at the same time, combining tools and techniques from the originally separated fields of discrete-variable and continuous-variable (optical) quantum information. An example for this would be our recent result demonstrating that continuous-variable quadrature squeezing helps to improve discrete-variable Bell measurements performed on dual-rail encoded photonic qubits using linear optics. Related to this, we have also been involved in the recent experiments of the University of Tokyo (Furusawa group), where single photons were squeezed and unsqueezed and where photonic qubits were deterministically teleported using techniques from continuous-variable teleportation based on on-demand quadrature squeezed-state entanglement and efficient quadrature Bell measurements (Quantum teleportation: Transfer of flying quantum bits at the touch of a button). The hybrid approach may also include atomic systems for storing and processing information, while light is the most convenient medium for communication.
- Quantum information schemes using linear optics
- Quantum information schemes based on continuous variables
- Optical hybrid (discrete-continuous, particle-wave) quantum information processing
- Long-distance quantum communication/quantum repeaters
- Measurement-based quantum computation/cluster states
- Optical quantum error correction codes
- Photonic entanglement (discrete, continuous, hybrid)