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Quantum Internet- Applications, Functionalities, Enabling Technologies, Challenges, and Research Directions

Amoldeep Singh, Kapal Dev, Harun Siljak, Hem Dutt Joshi, Maurizio Magarini

arXiv:2101.04427v2quant-phcs.CRcs.NI

TL;DR

Classical communication is vulnerable to eavesdropping, while quantum internet faces the challenge of transmitting fragile quantum information over long distances. This paper surveys quantum-internet concepts, technologies, functionalities, applications, and challenges. It concludes that entanglement-based teleportation and quantum repeaters are central to connecting distant nodes, with decoherence remaining a threat to communication.

  • Problem

    Long-distance quantum communication is difficult because environmental losses and decoherence affect qubits, while entanglement must be generated and distributed between distant nodes.

    Source: §I · p. 1, A. Decoherence · p. 21, C. Entanglement of Nodes across the… · p. 21

  • Method

    The paper surveys quantum-internet technologies and advances, introducing basic physics and reviewing network functionalities, applications, and challenges.

    Source: §VIII · p. 23

  • Results

    The survey concludes that quantum teleportation based on entanglement, supported by repeaters and local quantum memories, is central to connecting far-away network nodes.

    Source: §VIII · p. 23

  • Takeaways & Limitations

    The envisioned quantum internet combines remote classical and quantum nodes and uses quantum key distribution algorithms to exchange security.

    Source: §VIII · p. 23

Abstract

from arXiv · show

The advanced notebooks, mobile phones, and internet applications in today's world that we use are all entrenched in classical communication bits of zeros and ones. Classical internet has laid its foundation originating from the amalgamation of mathematics and Claude Shannon's theory of information. But today's internet technology is a playground for eavesdroppers. This poses a serious challenge to various applications that relies on classical internet technology. This has motivated the researchers to switch to new technologies that are fundamentally more secure. Exploring the quantum effects, researchers paved the way into quantum networks that provide security, privacy and range of capabilities such as quantum computation, communication and metrology. The realization of quantum internet requires quantum communication between various remote nodes through quantum channels guarded by quantum cryptographic protocols. Such networks rely upon quantum bits (qubits) that can simultaneously take the value of zeros and ones. Due to extraordinary properties of qubits such as entanglement, teleportation and superposition, it gives an edge to quantum networks over traditional networks in many ways. But at the same time transmitting qubits over long distances is a formidable task and extensive research is going on quantum teleportation over such distances, which will become a breakthrough in physically realizing quantum internet in near future. In this paper, quantum internet functionalities, technologies, applications and open challenges have been extensively surveyed to help readers gain a basic understanding of infrastructure required for the development of global quantum internet.

I. OUTLINE

The paper introduces quantum internet as a secure, privacy-oriented complement to classical internet, while identifying long-distance quantum communication as a challenge. It surveys the concepts, technologies, and applications needed to understand and develop global quantum networks.

I. OUTLINE

  • Qubits, entanglement, and no-cloning motivate quantum internet’s security and privacy, but decoherence makes long-distance transmission challenging,,,.The paper notes that quantum error-correcting codes and fault-tolerant techniques are used to mitigate noise,,,.Source: §I · p. 1

A. Quantum race

  • Quantum-computing efforts and public initiatives span industry, Europe, the United States, and China, alongside plans for quantum-network infrastructure,,,,,.The envisioned network connects remote nodes through entanglement and teleportation over fiber or free-space channels, with QEC to protect qubits from environmental effects.Source: A. Quantum race · p. 2

B. Motivation and Contribution

  • The survey addresses a gap left by reviews focused on individual topics, offering a generalized account for a wider audience.Its stated coverage includes quantum-mechanics preliminaries, quantum-internet functionalities, applications, challenges, and network components and their historical development.Source: B. Motivation and Contribution · pp. 2–3
  • The stated tutorial aims to make quantum-network components and their governing preliminaries understandable to readers without a quantum background.The contributions include basic quantum-mechanics concepts and tutorials on functionalities and possible applications.Source: B. Motivation and Contribution · p. 3

II. PRELIMINARIES

  • The paper presents quantum-mechanics concepts and qubit mathematics as preliminaries for understanding quantum computation and communication.It covers state-vector representation on the Bloch sphere and quantum gates for local operations and circuit manipulation.Source: §II · p. 4

A. Quantum Mechanics

The paper introduces quantum mechanics as a framework for understanding qubits and quantum communication. It explains qubit states geometrically and describes how superposition and measurement distinguish them from classical bits.

A. Quantum Mechanics

  • Quantum mechanics is presented as a mathematical framework for physical hypotheses involving single quantum systems, including qubits.The paper links qubit study to understanding quantum effects and potential secure communications,.Source: A. Quantum Mechanics · p. 4

1) State space and superposition principle:

2) Measurement of Quantum state:

3) Quantum No-Cloning:

The paper describes qubits as quantum information carriers that can be in superpositions of basis states, while measurement yields classical outcomes. No-cloning supports secure communication but also rules out copying or amplifying qubits to extend transmission distances.

3) Quantum No-Cloning:

  • No-cloning prevents copying or amplifying channel qubits, supporting secure communication while motivating quantum repeaters for long-distance transmission.The paper says attempted cloning can be detected, but no-cloning also blocks classical-style amplification or copying to prevent signal loss.Source: 3) Quantum No-Cloning · p. 5

B. Single Qubit system

  • A qubit can occupy a superposition of basis states, with complex amplitudes α and β representing probabilities for measurement outcomes.The passages describe an equal-amplitude state that yields 0 or 1 with probability 0.5 when measured.Source: B. Single Qubit system · p. 5
  • Measurement collapses a qubit state to 0 or 1, and the paper notes that the reason for this behavior is unknown.This is described as a limitation despite the qubit's theoretical capacity to carry infinite information.Source: B. Single Qubit system · p. 5

C. Multiple Qubits

Multiple qubits expand the computational basis exponentially, while Bell-state pairs provide the entanglement used in quantum-network tasks. Entanglement yields correlated outcomes but does not itself transmit information between remote nodes.

C. Multiple Qubits

  • Adding qubits increases the number of computational basis states exponentially, creating space for computations described as impossible with classical resources.A two-qubit system has four computational basis states.Source: C. Multiple Qubits · p. 6

1) Bell states or EPR Pairs:

  • Bell states are two-qubit states whose paired particles, called EPR pairs, support entanglement generation, distribution, and teleportation.The text identifies four Bell states and describes their measurement outcomes as correlated.Source: 1) Bell states or EPR Pairs · p. 6

2) Entanglement:

  • Entangled qubits produce correlated random outcomes, but entanglement provides mutual information rather than information exchange between remote nodes.The paper describes teleportation as transmitting an unknown quantum state with an EPR pair and local operations.Source: 2) Entanglement · p. 6
  • The paper connects multipartite entanglement to quantum error correction and describes GHZ states as distinct from Bell's theorem in the determinism of predicted outcomes.It also notes that adding particles increases the state-space dimension exponentially.Source: 2) Entanglement · p. 7

D. Quantum Gates

Quantum gates manipulate qubit states and form the building blocks of quantum circuits. The section also surveys entanglement generation, including photon-based parametric down conversion for remote nodes.

D. Quantum Gates

  • Quantum circuits use gates and wires to manipulate qubit information, including operations that entangle and teleport qubits between Alice and Bob.The section presents gates as building blocks for quantum computers.Source: D. Quantum Gates · p. 7

1) Single qubit quantum gates:

  • Single-qubit gates represent rotations about Bloch-sphere axes using Pauli matrices, including the NOT gate and a Hadamard transform.The text describes the Hadamard transform as obtainable through rotations about the Y and Z axes.Source: 1) Single qubit quantum gates · p. 7

2) Multiple Qubits Gate:

  • A CNOT gate uses control and target qubits: the target flips when the control is 1 and remains unchanged when it is 0.The passage points to a truth table and matrix transform for the operation.Source: 2) Multiple Qubits Gate · p. 7

A. Entanglement generation and distribution

  • Entanglement generation and distribution are key ingredients for exchanging information between remote nodes through quantum teleportation.The section introduces schemes for generating and distributing EPR pairs.Source: A. Entanglement generation and… · p. 7

1) Spontaneous Parametric Down Conversion:

  • Parametric down conversion uses a laser incident on a birefringent crystal to create correlated photons that travel separately to Alice and Bob.Photons are presented as promising because they can travel quickly over long fiber distances with little attenuation and moderate decoherence.Source: 1) Spontaneous Parametric Down… · p. 8

2) Single Atom Excitation by Laser Beam:

The paper surveys entanglement-generation schemes and qubit technologies alongside quantum teleportation, a process using shared entanglement and classical communication. It reports demonstrations over distances exceeding 1,200 km and notes that loss and decoherence can impair fidelity.

Entanglement generation schemes

1) Cavity quantum electrodynamics:

  • Cavity quantum electrodynamics couples matter qubits to optical or microwave cavity fields, with low-loss cavities enhancing the single-photon electric field.The review lists applications including atom-atom, atom-photon, and photon-photon entanglement.Source: 1) Cavity quantum electrodynamics · p. 8

2) Photonic qubits:

  • Photonic qubits can be controlled with traditional optical components and experience little decoherence, making them candidates for long-distance communication and distributed computation.The paper also notes weak birefringence and low photon absorption in free-space channels at optical frequencies.Source: 2) Photonic qubits · p. 8

3) Trapped ions:

  • Trapped ions offer coherence and low-crosstalk entangling gates, but scaling is constrained by how many entangling operations fit within coherence time.The paper identifies faster, higher-fidelity gates as necessary for large-scale computation on trapped-ion platforms.Source: 3) Trapped ions · p. 9

4) Solid state approach:

  • Solid-state qubits, including superconducting circuits, are presented as scalable options compatible with conventional RF and microwave components.The review describes the 53-qubit Sycamore processor and reports superconducting gate fidelities exceeding 99.9% for single-qubit and 99.5% for two-qubit gates.Source: 4) Solid state approach · p. 9, 5) Superconducting approach · p. 9

IV. QUANTUM INTERNET FUNCTIONALITIES

  • Quantum teleportation transfers a qubit state without physically transferring the particle that stores the qubit.The review describes the broader functionality set as including channels, repeaters, memories, QKD, and end nodes.Source: §IV · p. 9

A. Quantum Teleportation

  • Teleportation combines an entangled-pair quantum link with a classical link carrying two measurement bits, and reported demonstrations reached more than 1,200 km.The review also covers teleportation of different state types and identifies photon loss, environmental decoherence, and processing operations as sources of imperfections.Source: A. Quantum Teleportation · p. 10
  • Teleportation fidelity can be impaired by photon loss, environmental decoherence, or the sequence of operations used in processing.The review says the chosen teleportation technology affects fidelity and decoherence.Source: A. Quantum Teleportation · p. 10

1) Mathematical details:

Quantum teleportation uses shared entanglement and classical messages to transfer a quantum state from Alice to Bob. Alice measures her qubits, and Bob applies the corresponding correction to recover the original state.

1) Mathematical details:

  • Alice and Bob must share an EPR pair in a Bell state before teleporting the input data-qubit state.Alice applies CNOT to her two qubits and then jointly measures them; each of the four outcomes has a 25% probability.Source: 1) Mathematical details · pp. 10–11
  • Alice’s measurement result affects Bob’s qubit, and the classical measurement bits tell Bob which correction to apply.For outcome 00, Bob’s qubit already follows the original state; other outcomes require gate operations, including Pauli-X for one case.Source: 1) Mathematical details · p. 11
  • Bob recovers the original quantum state after applying the appropriate gate operations, completing teleportation between Alice and Bob.The procedure does not transmit information faster than light and therefore preserves the theory of relativity.Source: 1) Mathematical details · p. 11

2) Teleportation using Quantum Switch:

The quantum switch is presented as a teleportation resource for distributing entanglement through noisy channels. By placing channel order in superposition, it lets a message traverse more than one ordering of the channels.

2) Teleportation using Quantum Switch:

  • Noisy channels and decoherence limit entanglement distribution and reduce the efficiency of teleported information.The section motivates using superposed causal orders to make more efficient use of available resources over noisy channels.Source: 2) Teleportation using Quantum Switch · p. 11
  • The switch distributes entanglement between Alice and Bob by directing the entanglement-carrying qubit through the selected channel path.The figure describes a U gate directing the qubit, while a SWAP gate enables the entanglement-carrier operation.Source: Figure 10 · p. 11, 2) Teleportation using Quantum Switch · p. 11
  • A quantum switch uses a control qubit to place the order of two channels, C1 and C2, in superposition rather than fixing one order.A message may traverse C1→C2 or C2→C1; with a superposed control, both orders are enabled.Source: 2) Teleportation using Quantum Switch · p. 11
  • The paper identifies the quantum switch as a core quantum-web functionality and a key element in its teleportation process.Its implementation uses a Polarization Beam Splitter and Half-Wave Plates to switch between horizontal and vertical polarization states.Source: 2) Teleportation using Quantum Switch · pp. 11–12

B. Quantum Repeaters

Quantum repeaters address long-distance photon loss by dividing a network into shorter links and connecting those links through entanglement. The survey outlines repeater generations, protocols, and implementation approaches, including DLCZ and satellite-assisted links.

B. Quantum Repeaters

  • Quantum repeaters are placed between remote nodes to establish entanglement across long distances despite photon loss from channel attenuation and environmental factors.Unlike classical repeaters, they cannot copy or amplify qubits because of the no-cloning theorem.Source: B. Quantum Repeaters · p. 12
  • First-generation repeaters establish adjacent-node entanglement, swap it at stations, and purify weak states, but purification requires two-way classical acknowledgement.Second-generation schemes use QEC and one-way communication for purification, while third-generation schemes replace two-way signalling with one-way loss-tolerant codes.Source: B. Quantum Repeaters · p. 12
  • Most repeater implementations use discrete-variable encoding, while continuous-variable repeater protocols are a more recent line of work.The passage dates the first continuous-variable protocol to 2017–2018.Source: B. Quantum Repeaters · pp. 12–13
  • By creating entanglement on shorter segments and swapping it between intermediary stations, repeaters can entangle distant end nodes.The process recursively divides distance D into links of D/2, D/4, and smaller segments; the figure illustrates entangled intermediary qubits and swapping.Source: Figure 11 · p. 12, B. Quantum Repeaters · p. 13, Figure 12 · p. 13
  • DLCZ uses atomic ensembles as quantum memories and Raman-emitted photons to create entanglement between remote links.Single-photon detection connects the ensemble excitations; the emitted-photon and atomic-excitation correlation supports entanglement swapping.Source: B. Quantum Repeaters · p. 13
  • Quantum satellites such as Micius can support longer-distance free-space channels, where the vacuum improves fidelity and climatic diffraction effects are reduced.The survey also notes that developing quantum repeaters for a quantum web requires complex quantum technology.Source: B. Quantum Repeaters · p. 13

1) Workflow:

The workflow frames first-generation repeaters through an Alice–Bob quantum-cryptography example with entangled photons and channel losses. Its mathematical description includes joint Bell-state measurement notation for entanglement swapping.

1) Workflow:

  • The workflow considers Alice and Bob performing quantum cryptography with entangled photons over lossy channels that reduce the photon rate.The example seeks to keep channel noise as low as possible.Source: 1) Workflow · p. 13
  • The passage introduces a mathematical expression for the first-generation repeater example involving Alice, Bob, and photon loss.The supplied prose does not state additional steps represented by the expression.Source: 1) Workflow · p. 13
  • The notation marked in the workflow corresponds to a joint Bell-state measurement used for entanglement swapping.Source: 1) Workflow · p. 13

2) Entanglement swapping:

The section describes entanglement swapping as a way to extend entanglement across repeater stations, then surveys quantum-channel phases and free-space links. It highlights satellite distribution’s reach and stringent loss constraints.

2) Entanglement swapping:

  • Entanglement swapping uses a Bell-state measurement to entangle remaining particles, with multiple teleportation procedures across repeaters forming channels between end nodes thousands of kilometers apart.The section describes this as teleportation of entanglement between quantum states.Source: 2) Entanglement swapping · pp. 13–14

C. Quantum Channels

  • Quantum communication proceeds through encoding, channel evolution, and decoding, with the receiver measuring the state while accounting for error correction.Channels may use free space for long-distance transmission or fiber for relatively shorter distances; photon loss limits entanglement distribution.Source: C. Quantum Channels · p. 14

1) Free Space Channels:

  • Free-space links benefit from most photon loss occurring below 10–30 km of atmosphere, but atmospheric turbulence can affect OAM modes and mitigation techniques include adaptive optics, robust states, and optimal encoding.Laboratory experiments verified QKD protocols encoding with OAM modes.Source: 1) Free Space Channels · p. 14
  • Micius enabled entanglement distribution between ground stations more than 1,000 km apart, while successful ground-to-satellite quantum communication requires link attenuation no greater than 60 dB.Typical losses are reported at 30–40 dB; beam diffraction, pointing error, turbulence, absorption, and divergence contribute to channel loss.Source: 1) Free Space Channels · p. 14

2) Fiber Based Channels:

This block surveys fiber channels and quantum memories, then reviews QKD’s security rationale, distance limits, and key protocols. It contrasts fiber’s maturity with its attenuation constraints and describes BB84 and Ekert procedures.

2) Fiber Based Channels:

  • Optical fiber benefits from technological maturity and can preserve photon coherence, but polarization preservation and attenuation limit communication to a few hundred kilometres.An experiment created entanglement across 300 km of fiber; single-mode fibers are described as suited to high-precision quantum experiments.Source: 2) Fiber Based Channels · pp. 14–15

D. Quantum Memories

  • Quantum memories store and process qubits, convert between light and matter, and support synchronization and repeater-assisted range extension; reported transfer efficiency is 15%–25%.High-fidelity entanglement transfer remains a major challenge for network scalability.Source: D. Quantum Memories · p. 15

E. Quantum Key Distribution

  • QKD uses quantum cryptography to address key distribution and privacy, but increasing transmission distance raises fiber and atmospheric losses, reducing photon counts and key rates.No-cloning also restricts sending multiple information copies, contributing to practical distance limits of a few hundred kilometres.Source: E. Quantum Key Distribution · p. 15
  • Micius-related experiments reported QKD over 1,200 km, secure key generation between China and Europe 7,600 km apart, and 4,600 km communication integrating satellite links with Beijing–Shanghai fiber.Earlier QKD experiments were limited to a few hundred kilometres; increasing distance compounds losses and decoherence.Source: E. Quantum Key Distribution · pp. 15–16

1) Key Protocols:

  • BB84 sends single-qubit photon states, keeps bits where Alice and Bob chose the same basis, and checks for eavesdropping by revealing a random sample of bits.The passage reports BB84’s practical range as up to hundreds of kilometres over fiber or free-space atmospheric channels.Source: 1) Key Protocols · pp. 16–17
  • Ekert’s six-step protocol uses entangled photons, filters correlated measurement bits, and checks Bell’s inequality for evidence of eavesdropping before generating a secure key.The resulting key can be used in a symmetric procedure such as OTP; OTP requires a one-time key at least as long as the data.Source: 1) Key Protocols · pp. 16–17

2) Security of QKD:

The paper describes QKD security procedures and their attack assumptions, then connects end-node capabilities to possible applications. It presents secure communication and IoT protection as application areas while noting threats from quantum attacks on classical cryptography.

2) Security of QKD:

  • QKD protocols use correlated inputs and channel exchanges to produce secret keys, and should abort when inputs are tampered with; information reconciliation and privacy amplification improve imperfect key correlations.The paper says OTP, BB84, Ekert, and EPR protocols are secure against attacks on one qubit at a time, while simultaneous attacks on large blocks can compromise security.Source: 2) Security of QKD · pp. 17–18

F. End Nodes

  • End nodes may be quantum computers, memories, repeaters, or classical computers working with quantum computers, and require robust quantum-state storage until maximal entanglement is established.The section also identifies entanglement generators, repeaters, and quantum memories as end-node components for long-haul communication.Source: F. End Nodes · pp. 18–19

V. POSSIBLE APPLICATIONS

  • The paper surveys predicted quantum-internet applications including secure communication, blind computing, clock synchronization, longer-baseline telescopes, and the Internet of Things.It cautions that the technology is still in its infancy and its exact application areas cannot yet be predicted.Source: §V · p. 19

A. Secure Communication

  • QKD, QSS, QSDC, teleportation, and dense coding are presented as ways to detect hacking attempts and preserve privacy, with Micius-era QKD reported over thousands of kilometres.The paper also notes that sufficiently powerful quantum computers threaten classical public-key cryptosystems, while quantum cryptography could benefit IoT security.Source: A. Secure Communication · p. 19
  • QSDC sends secret information directly through a quantum channel without first generating keys, and the paper surveys variants using high-dimensional, multipartite, and hyper-entanglement.The passage also describes quantum signature, quantum dialog, and quantum direct secret sharing as related protocols.Source: A. Secure Communication · p. 19

B. Blind Computing

The section surveys blind quantum computation, clock synchronization, and quantum communication applications, then outlines practical challenges to quantum internet realization. It emphasizes that decoherence, imperfect operations, and long-distance entanglement distribution constrain these systems.

B. Blind Computing

  • Blind quantum computation lets users keep inputs and outputs secret while using a remote quantum computer, and can check whether computation is performed by a quantum processor.The one-way protocol lets Alice use a classical computer and a small quantum device.Source: B. Blind Computing · pp. 19–20

C. Clock Synchronization

  • Ticking Qubit Handshake can raise clock-synchronization accuracy to 100 ps, independent of message-delivery-time uncertainty.Existing protocols are reported to achieve better than 100 ns over distances exceeding 8000 km.Source: C. Clock Synchronization · p. 20

D. Longer Baseline of Telescope

  • Quantum repeaters can extend telescope-array baselines by reliably sending qubit states over noisy channels, potentially increasing information gathered over conventional arrays.Arrays with different baselines acquire more information than a single fixed-baseline pair.Source: D. Longer Baseline of Telescope · p. 20

VI. OPEN DIFFICULTIES AND CHALLENGES

  • The section identifies decoherence, teleportation and entanglement effects, design complexity, and measurement-induced state collapse as open difficulties.The interpretation of how probabilistic measurement outcomes become definite remains debated.Source: §VI · p. 20

A. Decoherence

  • Environmental interaction and photon loss cause decoherence, which irreversibly degrades teleportation fidelity and turns pure quantum states into mixed states.Perfectly isolating photons from the environment is described as impractical with current technologies.Source: A. Decoherence · p. 21

B. Imperfect Quantum Teleportation

  • Teleportation operations add imperfections beyond decoherence, and their multiplicative character is likened to classical fading rather than additive Brownian-motion noise.The passage says that these imperfections affect the teleported qubit.Source: B. Imperfect Quantum Teleportation · p. 21

C. Entanglement of Nodes across the Network

  • Distributing entanglement over long distances remains a key problem despite research progress, requiring repeaters, quantum memories, error-correction, and entanglement purification or distillation.The challenge includes storing qubit states at nodes and regularly updating them using quantum codes.Source: C. Entanglement of Nodes across the… · p. 21

D. Design complexity

  • No-cloning prevents quantum retransmission and direct use of classical error-correcting codes, making quantum error correction and network-layer design more complex.The passage locates this design complexity from error correction through medium access, routing, and layer-4 protocols.Source: D. Design complexity · p. 21

E. Measurement of Quantum states.

The survey presents quantum internet technologies and their open challenges, and outlines future directions for processors, networking, error correction, and hybrid systems. It concludes that satellite QKD has been achieved between distant ground stations while full realization still faces substantial design challenges.

E. Measurement of Quantum states.

  • Measurement collapses a qubit in superposition into one of its basis states, while how probabilistic outcomes become definite remains debated.The passage notes that the information storable and transmittable before measurement is still unknown.Source: E. Measurement of Quantum states · pp. 21–22

A. Evolution of Quantum Processors; E. Integrating Qubits with other technologies

B. Implementation of Trusted Repeater Network

  • Repeater networks use entangled intermediary nodes and entanglement swapping, while trust-free approaches include entanglement-based and measurement-device-independent QKD.The passage also names quantum network coding and quantum repeaters as ways to avoid the trusted-node assumption.Source: B. Implementation of Trusted Repeater… · p. 22

C. Quantum Error Correcting Codes

  • Decoherence-free subspaces store information across multiple qubits, but identifying them in complex systems is difficult and motivates further QEC research.Dynamic decoupling applies radio-frequency pulses to manipulate the non-unitary component of a quantum system.Source: C. Quantum Error Correcting Codes · p. 22

D. Exploring Interface between DV and CV

  • Discrete-variable states encode information in finite basis states, whereas continuous-variable states use optical-field quadrature variables in an infinite-dimensional Hilbert space.The survey calls for research at the interface of the two approaches to extract features from both.Source: D. Exploring Interface between DV and CV · p. 22

F. Exploration of Solid-state memories

  • The survey proposes integrating superconducting processors with solid-state quantum memories, whose spin ensembles can remain coherent for hours at cryogenic temperatures.It identifies on-chip teleportation between a superconducting qubit and a nitrogen-vacancy center as a step to investigate.Source: F. Exploration of Solid-state memories · p. 23

G. Quantum-classical synergy

  • Future quantum internet is described as working alongside classical internet, using classical channels for teleportation data and QKD reconciliation and privacy amplification.The passage envisions BQC-protected quantum cloud services and secure links to classical devices.Source: G. Quantum-classical synergy · p. 23

VIII. CONCLUSION

  • Quantum satellites have achieved QKD between two far-away ground stations, motivating efforts to build a full-blown quantum internet.The conclusion identifies teleportation based on entanglement generation and distribution as the most challenging requirement.Source: §VIII · p. 23

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