# Quantum Teleportation

Quantum teleportation is a process by which the state of a quantum system can be transmitted from one location to another, with the help of two entangled particles and classical communication. Entanglement is a crucial resource for quantum teleportation, as the entangled particles exhibit correlations that allow the state of one particle to be determined by the state of the other, regardless of the distance between them.

Quantum teleportation can achieve perfect fidelity, meaning the state is transferred without alteration. It does not violate the no-cloning theorem, which states that an arbitrary unknown quantum state cannot be copied exactly, as the original state is destroyed during the teleportation process. Alice's measurement collapses the entangled state and provides information that Bob needs to reconstruct the teleported state.

**What is Quantum Teleportation**

Because of the science fiction genre, quantum teleportation almost has to be defined more by what it is not, rather that what it is. Quantum teleportation, for example, does not involve the physical transportation of particles themselves. In fact, it does not involve the instantaneous or physical transportation of objects in any way. Instead, the process only involves the transfer of quantum information, and this process relies on entanglement and classical communication. With **quantum entanglement teleportation** becomes possible, but classical communication is needed to both decode the teleported information, as well as to not violate faster-than-light (FTL) communication prohibitions.

Also unlike science fiction, the notion of a **quantum teleportation experiment** is not fantasy. Nor is it just a theory. In fact, quantum teleportation has been experimentally demonstrated over two-and-a-half decades using various physical systems, including photons, atoms, and superconducting circuits. In an article titled “The Mysteries Of Quantum Teleportation Explained,” The Quantum Insider lists some of the most notable quantum teleportation experiments:

- In 1997, Anton Zeilinger’s team teleported a quantum state using photons
- In 2004, NIST and the University of Innsbruck teleported a quantum state between atoms
- In 2008, a University of Tokyo team used photons to teleport over several kilometers
- In 2015, a NIST team used photons to teleport information over 100 kilometers

You don’t need a laboratory to verify this research, by the way. You can teleport quantum information and verify the success of your experiment using a cloud-accessible quantum computer.

**The Quantum Teleportation Process**

The process of quantum teleportation begins with an entangled pair of particles shared between two parties, often referred to as Alice and Bob. Alice wants to teleport the state of a qubit to Bob. By performing specific measurements on her particles and sending the results to Bob via classical communication, Bob can apply certain operations to his entangled particle to recreate the exact state that Alice wanted to teleport.

The simplest **quantum teleportation circuit** requires only three qubits. Alice puts her qubit into a quantum superposition using what is known as a Hadamard gate, and then she entangles her qubit with Bob’s qubit using what is called a controlled-NOT gate. Alice then takes a third qubit, which has the quantum state to be teleported, and she entangles that qubit with her qubit. She then measures her two qubits in two different bases, which destroys her quantum information but gives her the classical information she needs to provide to Bob. Upon receipt, Bob uses the classical information to perform operations on his qubit that then allows him to use the teleported quantum state for whatever purposes. Because Bob had to wait for the classical information to arrive, no physics laws were violated.

**Current Challenges and Future Prospects**

Implementing quantum teleportation in practical scenarios requires precise control over entanglement, accurate measurements, and error-free classical communication. Research continues to focus on improving the efficiency, reliability, and scalability of quantum teleportation, as well as integrating it into emerging quantum technologies.

Quantum teleportation is more than a fascinating theoretical concept; it represents a fundamental building block of quantum information processing. Its discovery has deepened our understanding of quantum entanglement and has paved the way for advances in quantum communication and quantum networking, as well as in quantum computation; it forms the basis for certain quantum algorithms and protocols.

Quantum teleportation is a remarkable demonstration of the unique properties of quantum systems. It showcases the power of entanglement and provides a practical tool for transmitting quantum information. As technology advances, quantum teleportation may play a vital role in the development of global quantum networks and secure communication systems. The Quantum Insider titled “The Mysteries Of Quantum Teleportation Explained” lists its top three applications:

- A teleportation-based quantum Internet may connect quantum computers for the secure transmission of quantum information, as well as to enable distributed quantum computation
- Teleportation-based quantum sensors could enable higher precision measurements for both sensing and metrology applications
- Teleportation-based networks could use quantum key distribution (QKD) to secure communications between remote parties

A novel application, related but different, is **quantum energy teleportation**. At a high level, teleporting energy and information seems quite similar, after all measuring a qubit reveals which energy level it has been found in. The distinctions between teleporting energy and teleporting information, however, is beyond the scope of this definition.

For more information, the Science Direct “Quantum Teleportation” page lists a number of papers, including some of the most recent research into this topic.