Title: 1G, 2G, 3G: Evolution of Quantum Repeaters
Type: Webpage
Source: https://www.aliroquantum.com/blog/1g-2g-3g-evolution-of-quantum-repeaters
1G, 2G, 3G: Evolution of Quantum Repeaters
For near-term quantum networks, characterised by high error rates aand short memory times, quantum repeaters will rely on entanglement purification and entanglement swapping.
Main sources of errors in quantum networks:
- Loss errors: Qubits are lost when travelling on connections
- Operation errors: Noisy operations reduce quality of qubits on repeaters and endpoints
Choice of repeater is contexty dependent: dependent on available hardware and bandwidth requirements. The distinction among the three generations is determined by methods of handling errors.
Based on technique called heralding to cope with high errors rates and near-term quantum devices.
A heralding network works by testing performance in real-time and only proceeds when a protocol succeeds. The network sends a classical signal indicating success and thus the network can proceed. This is heralding.
Heralding is used to correct for both errors.
- Loss errors: Heralded Entanglement Generation (HEG) ensures succeessful entanglement by repeating attemps until a classical signal confirms entanglement has succeeded. Success signal is sent to bot endpoints to indicate success.
- Operation errors: Heralded Entanglement Purification (HEP) takes in several low fidelity entangled pairs to produce a single high fidelity entangled pair, with a classical signal to each end-point indicating success.
maintains entanglement generation at high qualities.
Costs the networks' Bandwidth. Bandiwdth is determined by thre number of entangled pairs that can be generated in a given amount of time.
The heralding messages slows down quantum networks, because each end-point must wait to receive the classical message. Consequently, endpoints in long distances will have lower bandwidth.
Introduces quantum error correction (QEC). QEC replaces entanglement purification. QEC produces a single high fidelity pair by encoding it in a large number pairs.
This has impact on rate but without the round-trip classical signalling needed in heraleded entanglement purification. Hence, bandwidth is increased.
QEC requires high-quality hardware, which isn't available in our NISQ era devices.
It primarily scales the quantum network. QEC is being used to manage loss errors.
Instead of iteratively building entanglement followed by teleportation, qubits can be encoded directly into clusters and passed across a network, eliminating need for heralding.
Hardware requirements are extremely high, but it unlocks the full scaling capability of quantum internet.
Researchers focusing on developing First Gen quantum repeaters using heralded entanglement generation and purification. 1st Gen repeaters have applications is secure communication and High-Performance Computing (HPC).
- https://www.aliroquantum.com/blog/3-quantum-repeater-advances-in-2021 -
3 quantum repeater advances in 2021