Quantum computers use “qubits” which hold both zero and one at the same time. A quantum network can transmit them via quantum entanglement.
Quantum entanglement is a phenomenon in quantum mechanics where particles become correlated in such a way that the state of one particle is directly linked to the state of another, regardless of the distance between them.
Imagine you have two particles, say photons, that are entangled. When they're created or interact, their properties, like spin or polarization, become interconnected. This means that if you measure one particle's property, the result you get is completely random until you measure the corresponding property of the other particle. Once you measure the second particle, its state is instantly determined, and it will always be opposite or complementary to the state of the first particle. This observation of one particle will affect the state of its entangled partner, no matter how far away that other particle is.
You can use that to encrypt information. If a sender wants to send a message to a receiver, each would receive one of a pair of entangled photons. Measuring those photons’ states would give both a unique key, which is used to encrypt a message, and in turn to decrypt it. If somebody tried to tap in for the key, that would influence the photons, and both parties would be alerted. This method of encryption is theoretically unhackable as entangled photons can’t be covertly read without disrupting their content. This could be used over the internet or even InterPlaNet in Type 1 cultures.
With the speed of light being the only limiting factor, it is possible to create pure (extremely fast) bandwidth of transmission of information between entangled particles. This process is described in teleportation.
An experiment with quantum-entangled photons found that the slowest possible speed for quantum interactions is 10,000 times the speed of light. If this is true, it is possible in the future to make quantum entanglement communication (QEC) devices that send information many times faster than light. An argument against this phenomenon would be that "Teleportation is not instantaneous; it transmits in lightspeed. So, technically whatever was transmitted “felt” it happened in zero subjective time, but in objective time it took the amount of time required for electromagnetic waves to traverse the distance." Also, the No-communication theorem states that, "during measurement of an entangled quantum state, it is not possible for one observer, by making a measurement of a subsystem of the total state, to communicate information to another observer. The theorem is important because, in quantum mechanics, quantum entanglement is an effect by which certain widely separated events can be correlated in ways that, at first glance, suggest the possibility of communication faster-than-light."
An experiment showed that that entanglement also possibly occur across time. The discussion is here.
These experiments could lead one to think that entanglement can transcend all boundaries of spacetime and gravity, possibly even within the 11 dimensions of our omniverse.
Real world engineering[]
- Spontaneous Parametric Down‑Conversion (SPDC): A laser pumps a nonlinear crystal, converting individual photons into pairs of lower-energy photons whose polarizations are quantum-entangled.
- Atomic Cascade Emission: certain atoms or ions excited to high-energy states can cascade down in stages, emitting two or more photons. These emitted photons can become entangled in polarization or timing.
- Quantum dot or biexcitons: Semiconductor quantum dots are engineered so that when excited, they emit entangled photon pairs via biexciton decay. These sources can be electrically triggered (“on-demand”) and produce high-fidelity entangled photons.
- Free electron mediated generation: Energetic electrons interact with nanoscale photonic waveguides to emit plasmon or photon pairs. These paired excitations can be entangled in momentum and energy, and are detectable via electron energy loss signals.
- Ion traps, optical lattices, and cold atoms: Atoms or ions are trapped and controlled with lasers; then quantum gates are applied to entangle their internal (spin) states. These setups are used for deterministic entanglement in quantum computing platforms.
- Cooper-pair splitting in superconductors: Electrons in Cooper pairs within superconductors are inherently entangled. By splitting these pairs into separate leads (using single-electron transistors), spatially separated entangled electrons are created and converted into entangled photons.
- Dissipation-based steady-state entanglement is engineered via a controlled interaction with a tailored environment (e.g. lasers plus magnetic fields). This continuously produces entangled states between macroscopic atomic ensembles, even at room temperature.
- Entanglement swapping: Two independently generated entangled pairs are set up so that a joint measurement on one particle from each pair can entangle the remaining two particles, even if they never directly interacted. This technique is foundational for building quantum networks.
Some uses[]
News[]
- Alain Aspect, Anton Zeilinger and John Clauser share the 2022 Nobel Prize in Physics for their research on quantum entanglement.
- Quantum entanglement expands to city-sized networks