Quantum Teleportation: Exploiting Entanglement & No Cloning Theorem

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Discussion Overview

The discussion revolves around the concept of quantum teleportation, particularly focusing on the role of entanglement and the implications of the no cloning theorem. Participants explore the mechanics of quantum teleportation, its comparison to classical methods, and the nature of information transmission versus matter transfer.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants express confusion about how quantum teleportation works and its implications for conservation laws, particularly regarding the no cloning theorem and the destruction of the original state.
  • Others clarify that "destroying" the original state refers to changing its measurable properties rather than annihilating its matter, emphasizing that information is what is transmitted, not physical matter.
  • There is a discussion about the directionality of quantum teleportation, with some arguing it is directionless while others assert that the process has a clear sender and receiver role, particularly during the measurement and correction steps.
  • Participants draw parallels between quantum teleportation and classical encryption methods, such as the one-time pad, to aid understanding of the process.
  • Some participants note that the no cloning theorem implies the original matter is altered rather than destroyed, contributing to the ongoing debate about the implications of these concepts.

Areas of Agreement / Disagreement

Participants express differing views on the directionality of quantum teleportation and the interpretation of the no cloning theorem. There is no consensus on these points, and the discussion remains unresolved.

Contextual Notes

Participants highlight the complexity of quantum teleportation and the nuances in understanding the implications of entanglement and the no cloning theorem. The discussion reflects varying interpretations and assumptions about these concepts.

Who May Find This Useful

This discussion may be of interest to those studying quantum mechanics, quantum information theory, or anyone curious about the implications of quantum teleportation and entanglement.

Trollfaz
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Quantum teleportation exploits entanglement but I don't really know how it works. And I heard that the no cloning theorem says that the original state must be destroyed. Wouldn't it violate the principle of conservation of energy mass?
 
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I don't think there is any such violation. "Destroying" the original state doesn't mean destroying its matter. It means changing the state of the original system, in such a way that it cannot be measured again with the same result. On the receiving end, say, on Mars, the copy is made from matter on Mars; the telportation just means that that matter is put into a state that mirrors the original state of the matter on Earth.

What is transmitted from Earth to Mars is information, not matter.
 
Quantum teleportation is directionless. Nothing is transmitted from point A to B any more than from B to A. At least, not as far as any experiment can differentiate.
 
Quantum teleportation is really really similar to a classical encryption method called the one-time pad. That's one way to understand what teleportation is doing.

Another way to understand what teleportation is doing is by starting with a quantum circuit that swaps two qubits and making trivially correct changes to the circuit until you're left with teleportation.

quantum-teleportation-circuit.png


The measurement is what "destroys" the sender's "copy" of the state. But this is a bit misleading; even if you omitted the measurement, the teleportation circuit would simply replace the sender's qubit's state with the state ##|0\rangle + |1\rangle##. There's never actually a true copy of the state.

DrChinese said:
Quantum teleportation is directionless. Nothing is transmitted from point A to B any more than from B to A. At least, not as far as any experiment can differentiate.

No, it definitely has a direction. The sender is the one doing the Bell basis measurement and broadcasting the results, and the receiver is the one applying a fixup operation based on the outcome of the measurement.

The entanglement used by teleportation is directionless, though. An EPR pair can be used to send a qubit in either direction. Also you could easily create a (more complicated and requiring more entanglement) two-way teleportation that was completely symmetric and swapped a qubit at A for a qubit at B.
 
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The no cloning theorem states that the original matter must be altered, not destroyed.
 
Strilanc said:
No, it definitely has a direction. The sender is the one doing the Bell basis measurement and broadcasting the results, and the receiver is the one applying a fixup operation based on the outcome of the measurement. ... The entanglement used by teleportation is directionless, though. ...

No argument, and nice reference example. I misspoke.
 
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