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6CCVD Research

Investigating Imperfect Cloning for Extending Quantum Communication Capabilities

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2023-09-14
JournalSensors
AuthorsMasab Iqbal, Luis Velasco, Nelson Costa, Antonio Napoli, JoĂŁo Pedro
InstitutionsUniversitat PolitĂšcnica de Catalunya, Instituto Superior TĂ©cnico
Citations6
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”

This research investigates methods to establish reliable and multi-destination quantum communication by circumventing the fundamental limitation of the no-cloning theorem using imperfect quantum copies.

  • Core Problem Addressed: The no-cloning theorem prevents perfect qubit retransmission (Automatic Repeat Request, ARQ) and Point-to-Multipoint (P2MP) communication in quantum networks.
  • Proposed Solution: Implementation of the Universal Quantum Copying Machine (UQCM) to generate imperfect, optimal clones (maximum fidelity of 0.833 for two clones).
  • Protocols Developed: Quantum Automatic Repeat Request (QARQ) for reliable transmission and Quantum P2MP (QP2MP) for broadcasting.
  • Technology Comparison: Three transport methods were simulated on the Nitrogen-Vacancy (NV) center platform: Direct Transmission (DT), Teleportation (TP), and Telecloning (TC).
  • Performance Metric: Telecloning (TC) provides the highest fidelity for both QARQ and QP2MP, significantly outperforming TP and DT, especially over long distances.
  • Complexity Trade-off: TC is the most complex protocol, requiring the highest Quantum Cost (36 gates) compared to TP (21 gates) and DT (9 gates).
  • QARQ Optimization Insight: Numerical analysis shows that increasing the number of clones does not always improve the probability of successful qubit recovery, due to the associated degradation in clone fidelity.

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
Max UQCM Fidelity (2 clones)0.833NoneTwo-state input qubit
Max UQCM Fidelity (3 clones)0.77NoneTwo-state input qubit
Max UQCM Fidelity (4 clones)0.75NoneTwo-state input qubit
QKD Fidelity Threshold0.8NoneMinimum required fidelity for basic Quantum Key Distribution
Quantum Memory Decay Time (T1)10hoursNV center platform simulation
Quantum Memory Decoherence Time (T2)1secondNV center platform simulation
Gate Depolarization Probability (dp)0.01NoneAssumed for all quantum gates
Single-qubit Gate Duration (X, Z, H)5nsNV center implementation
CNOT Gate Duration20”sNV center implementation
Measurement Duration3.7”sNV center implementation
Telecloning (TC) Quantum Cost36NoneHighest complexity protocol
Teleportation (TP) Quantum Cost21NoneIntermediate complexity protocol
Direct Transmission (DT) Quantum Cost9NoneLowest complexity protocol
TP Qubit Requirement7QubitsHighest qubit requirement

Key Methodologies

Section titled “Key Methodologies”

The feasibility and performance of QARQ and QP2MP were evaluated using the NetSquid quantum network simulator, modeling the NV center platform.

  1. Simulation Environment: NetSquid [22] was used for precise modeling of quantum physical devices and discrete event simulation of network protocols.
  2. Hardware Platform: Nitrogen-Vacancy (NV) centers in diamond were selected due to their long coherence times and suitability for quantum Internet applications.
  3. Noise Modeling:
    • Quantum gates (Single-qubit, CNOT, Rotation) were modeled with depolarizing noise, assuming a depolarization probability (dp) of 0.01.
    • Quantum memory utilized the T1T2 noise model, with T1 = 10 hours (decay) and T2 = 1 second (decoherence).
    • Channel decoherence was modeled using depolarization probability per km of fiber.
  4. Cloning Implementation: The Universal Quantum Copying Machine (UQCM) circuit was designed using Y-rotation and CNOT gates to generate optimal imperfect clones before transmission.
  5. Protocol Implementation (QARQ/QP2MP):
    • Direct Transmission (DT): Clones are generated, and one is sent directly through the lossy quantum channel; others are stored in memory (QARQ).
    • Teleportation (TP): Entanglement pairs are pre-distributed. The sender performs Bell measurements on the source qubit and one part of the entanglement pair, sending classical results for correction.
    • Telecloning (TC): A specialized telecloning state is prepared and distributed. The sender performs Bell measurements, and classical results are sent for correction.
  6. Complexity Analysis: Quantum Cost (number of 1x1 and 2x2 quantum gates) and Qubit Requirement (total number of bits needed) were calculated for DT, TP, and TC circuits.

Commercial Applications

Section titled “Commercial Applications”

The successful implementation and optimization of QARQ and QP2MP protocols are critical enablers for next-generation quantum infrastructure.

  • Quantum Internet Infrastructure: Provides the fundamental protocols necessary for reliable, long-distance communication between quantum computers, overcoming the limitations of qubit loss and the no-cloning theorem.
  • Distributed Quantum Computing: Enables Point-to-Multipoint (QP2MP) communication, allowing a single source qubit state to be broadcast to multiple computational nodes for parallel processing or state sharing.
  • Fault-Tolerant Quantum Networks: QARQ provides a mechanism for error control and retransmission, essential for maintaining high fidelity in Noisy Intermediate Scale Qubits (NISQ) era devices.
  • Quantum Key Distribution (QKD) Reliability: QARQ can be integrated into QKD systems to significantly improve the probability of successful key exchange by recovering lost qubits, ensuring fidelity remains above the required threshold (e.g., 0.8).
  • Solid-State Quantum Hardware: The simulation results, based on the NV center platform, directly inform the design and optimization of protocols for solid-state quantum devices, which are promising candidates for scalable quantum networks.
View Original Abstract

Quantum computing allows the implementation of powerful algorithms with enormous computing capabilities and promises a secure quantum Internet. Despite the advantages brought by quantum communication, certain communication paradigms are impossible or cannot be completely implemented due to the no-cloning theorem. Qubit retransmission for reliable communications and point-to-multipoint quantum communication (QP2MP) are among them. In this paper, we investigate whether a Universal Quantum Copying Machine (UQCM) generating imperfect copies of qubits can help. Specifically, we propose the Quantum Automatic Repeat Request (QARQ) protocol, which is based on its classical variant, as well as to perform QP2MP communication using imperfect clones. Note that the availability of these protocols might foster the development of new distributed quantum computing applications. As current quantum devices are noisy and they decohere qubits, we analyze these two protocols under the presence of various sources of noise. Three major quantum technologies are studied for these protocols: direct transmission (DT), teleportation (TP), and telecloning (TC). The Nitrogen-Vacancy (NV) center platform is used to create simulation models. Results show that TC outperforms TP and DT in terms of fidelity in both QARQ and QP2MP, although it is the most complex one in terms of quantum cost. A numerical study shows that the QARQ protocol significantly improves qubit recovery and that creating more clones does not always improve qubit recovery.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2022 - Cost-effective Ml-powered polarization-encoded quantum key distribution [Crossref]
  2. 2018 - Quantum internet: A vision for the road ahead [Crossref]
  3. 2022 - LPsec: A fast and secure cryptographic system for optical connections [Crossref]
  4. 1982 - A single quantum cannot be cloned [Crossref]
  5. 2014 - Performance Evaluation of Light-tree Schemes in Flexgrid Optical Networks [Crossref]
  6. 2018 - Quantum computing in the NISQ era and beyond [Crossref]
  7. 1995 - Scheme for reducing decoherence in quantum computer memory [Crossref]
  8. 2019 - Quantum error correction: An introductory guide [Crossref]
  9. 2021 - Protocols for packet quantum network intercommunication [Crossref]

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