Alice has a qubit in state |psi> = cos(theta/2)|0> + e^(i*phi)*sin(theta/2)|1>. She wants to send this state to Bob, but she can only send classical bits.
Look for: The Bloch sphere shows the dashed target |psi> — this is what Bob should end up with. Only the first two bars (|000> and |001>) are lit because only q0 has been prepared.
Teleportation isn't science fiction — it's a foundational primitive in quantum technology:
Quantum networks: Teleportation is how quantum repeaters will relay qubits across long distances, enabling a future quantum internet.
Error correction: Fault-tolerant quantum computers use teleportation-like circuits to move logical qubits without exposing them to errors.
Gate teleportation: Hard-to-implement gates can be “pre-loaded” into entangled states and applied via teleportation, a key trick in scalable architectures.
“Does this send information faster than light?”
No. Bob's qubit is random until he receives Alice's 2 classical bits, which travel at light speed or slower. Without the correction, Bob just has noise. Entanglement alone can't carry a message.
“Is the qubit copied?”
No — the no-cloning theorem forbids it. Alice's qubit is destroyed by measurement. The state is transferred, not duplicated. After teleportation, only Bob has |psi>.
“Does matter move from Alice to Bob?”
No. Nothing physical travels. The quantum state (information about amplitudes and phases) is transferred to Bob's pre-existing qubit. Think of it as moving a file between computers, not shipping a hard drive.
Quantum teleportation transfers the state of one qubit to another using a shared entangled pair and two classical bits of communication. No physical particle moves — only quantum information. The protocol was proposed by Bennett et al. in 1993 and first demonstrated experimentally in 1997.
The steps are: Alice and Bob share a Bell pair. Alice performs a Bell measurement on her qubit and the state to teleport, then sends the two classical bits of result to Bob. Bob applies a correction gate conditioned on those bits, recovering the original state perfectly.
Teleportation is not faster-than-light communication — the classical bits must travel conventionally. But it is a building block for quantum networks, error correction, and measurement-based quantum computing.