| quantum teleportation protocol | |
|---|---|
| Name | Quantum teleportation |
| Caption | Schematic of a basic quantum teleportation circuit |
| Field | Quantum information science |
| Invented | 1993 |
| Inventor | Charles H. Bennett et al. |
| First demo | 1997 |
| First demo by | Dik Bouwmeester et al. |
quantum teleportation protocol The quantum teleportation protocol is a method for transferring the quantum state of a particle from one location to another without moving the physical particle itself. It uses quantum entanglement and classical communication to reconstruct an unknown qubit state at a distant site, and underpins protocols in quantum communication and quantum computing where state transfer and resource distribution are required.
Quantum teleportation protocol demonstrates nonlocal correlations predicted by quantum mechanics and operationalizes entanglement as a transferable resource. First formalized in the 1993 paper by Charles H. Bennett and collaborators, the protocol shows how a sender ("Alice") and a receiver ("Bob") can use a pre-shared entangled pair and two bits of classical communication to transfer an unknown quantum state without violating the no-cloning theorem. The protocol is foundational for proposed architectures of the quantum internet and for tasks including quantum key distribution augmentation, entanglement swapping, and modular quantum computing.
The protocol relies on a set of core concepts in quantum information theory: the qubit as the basic information carrier, maximally entangled two-qubit states known as Bell states (e.g., |Φ+⟩, |Ψ−⟩), and the constraints imposed by the no-cloning theorem and quantum measurement. Entanglement, originally studied in the EPR paradox by Einstein, Podolsky, and Rosen and formalized into bipartite resource theories, is used as a channel resource characterized by measures such as entanglement entropy and concurrence. The formal description employs quantum gates (e.g., Hadamard gate and CNOT gate) and projective measurement in the Bell basis to enact a joint measurement that correlates the sender's unknown state with one half of the shared entangled pair.
In the canonical three-qubit protocol, Alice holds the unknown qubit |ψ⟩ and one qubit of an entangled pair; Bob holds the other. Alice performs a Bell state measurement on her two qubits, projecting them onto one of four Bell states and collapsing Bob's qubit into a corresponding rotated version of |ψ⟩. Alice transmits two classical bits to Bob, who applies one of four Pauli matrices (I, X, Z, XZ) as corrective unitaries to recover |ψ⟩. The standard circuit uses a CNOT gate followed by a Hadamard gate and two single-qubit measurements; controlled unitaries on Bob's side complete the teleportation. This circuit model aligns with descriptions in the quantum circuit formalism and can be embedded within larger networks of quantum error correction and entanglement purification.
Extensions adapt the protocol to different resource regimes. Continuous-variable quantum information implementations replace qubits with field quadratures and use squeezed states and homodyne detection to teleport coherent states; notable theoretical work by Samuel L. Braunstein and H. J. Kimble advanced these methods. Multi-qubit and multipartite entanglement teleportation protocols teleport entangled or logical states across cluster states and graph states for measurement-based quantum computation. Port-based teleportation is a variant enabling unitary-free recovery at the cost of many entangled pairs and higher resource scaling; it has applications in programmable quantum processors and in theoretical studies of quantum channel simulation. Protocols incorporating entanglement swapping permit extended-range teleportation via quantum repeater architectures developed by groups such as those at Los Alamos National Laboratory and Delft University of Technology.
First experimental demonstrations used single-photon polarization states by teams led by Dik Bouwmeester (1997). Subsequent implementations employed a diversity of platforms: photonic systems with spontaneous parametric down-conversion sources and integrated photonics (e.g., work at University of Bristol and IBM), trapped-ion experiments at Innsbruck and University of Maryland, superconducting qubits at Google and IBM Quantum, and solid-state systems such as nitrogen-vacancy centers in diamond and quantum dots (e.g., groups at University of Basel). Long-distance teleportation over optical fiber and free-space was demonstrated by teams including China's Micius satellite project, achieving ground-to-satellite links. Continuous-variable teleportation experiments were advanced by groups at Caltech and NIST.
Teleportation fidelity depends on the quality of the shared entanglement, measurement efficiency, classical communication latency, and decoherence in storage or transmission channels. Practical errors include photon loss, imperfect gate fidelities (characterized in superconducting and trapped-ion platforms), detector inefficiency, mode mismatch in optics, and finite squeezing in continuous-variable systems. Theoretical bounds relate achievable fidelity to entanglement measures and the quantum channel capacity; fault-tolerant integration requires combining teleportation with quantum error correction and entanglement purification protocols to mitigate noise.
Quantum teleportation is a primitive for the quantum internet enabling remote entanglement distribution, building blocks for quantum repeaters, and modular architectures in distributed quantum computation. Teleportation-based gate teleportation and measurement-based quantum computing leverage teleportation to implement logical operations and to move encoded qubits between error-corrected registers. In cryptography, teleportation concepts intersect with device-independent quantum key distribution and protocols for blind quantum computation. The continued refinement of teleportation protocols influences standards and efforts by institutions such as IEEE working groups and large research collaborations in quantum technologies.
Category:Quantum information science Category:Quantum teleportation