Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:quant-ph/0011073 · Physical Review A

Quantum cloning and distributed measurements

Dagmar Bruß, John Calsamiglia, Norbert Lütkenhaus

Published Mar 20, 2001• 32 citations
arXivHTMLPDF

Abstract

We study measurements on various subsystems of the output of a universal $\stackrel{\ensuremath{\rightarrow}}{1}2$ cloning machine, and establish a correspondence between these measurements at the output and effective measurements on the original input. We show that one can implement sharp effective measurement elements by measuring only two out of the three output systems. Additionally, certain complete sets of sharp measurements on the input can be realized by measurements on the two clones. Furthermore, we introduce a scheme that allows us to restore the original input in one of the output bits, by using measurements and classical communication---a protocol that resembles teleportation.

DOI
10.1103/physreva.63.042308

Related papers

Experimental reversion of the optimal quantum cloning and flipping processes

Fabio Sciarrino, Veronica Secondi, F. De Martini

The quantum cloner machine maps an unknown arbitrary input qubit into two optimal clones and one optimal flipped qubit. By combining linear and nonlinear optical methods we experimentally implement a scheme that, after the cloning transformation, restores the original input qubit in one of the output channels, by using local measurements, classical communication, and feedforward. This nonlocal method demonstrates how the information on the input qubit can be restored after the cloning process. The realization of the reversion process is expected to find useful applications in the field of modern multipartite quantum cryptography.

arXiv:quant-ph/0504212•Physical Review A•Apr 19, 2006•6 citations

Quantum inputs in the prepare-and-measure scenario and stochastic teleportation

Elna Svegborn, Jef Pauwels, Armin Tavakoli

Abstract We investigate prepare-and-measure scenarios in which a sender and a receiver use entanglement to send quantum information over a channel with limited capacity. We formalise this framework, identify its basic properties and provide numerical tools for optimising quantum protocols for generic communication tasks. The seminal protocol for sending quantum information over a classical channel is teleportation. We study a natural stochastic generalisation in which the sender holds N qubits from which the receiver can recover one on demand. We show that, if the classical communication is allowed to exploit extremal non-signalling correlations, then two bits of communication suffice to solve this task exactly for any N . We then consider entanglement-based protocols and show that these can be constructed systematically by leveraging connections to several well-known quantum information primitives, such as teleportation, cloning machines and random access coding. In particular, we show that by using genuine multi-particle entangled measurements, one can construct a universal stochastic teleportation machine, i.e. a device whose teleportation fidelity is independent of the quantum input.

arXiv:2504.00162•Quantum Science and Technology•Feb 5, 2026•0 citations

Is It Possible To Clone Using An Arbitrary Blank State?

Roy, A, Ujjwal Sen, Sen, U

We show that using a fixed cloning machine, whether deterministic inexact or probabilistic exact, one can take an arbitrary blank state. Quantum information cannot be cloned. There cannot exist a machine which can produce two (or more) exact copies of an arbitrary state in a deterministic manner [1]. Replication is not allowed even when the input state is taken at random from a given set of two non-orthogonal states [2]. It has been further shown that probabilistic cloning is not possible if the input state is from a given linearly dependent set [3]. Henceforth we deal explicitly with qubits although all the results can be extended to higher dimensions. Although exact cloning is not possible, one can approximately clone an arbitrary input state [4, 5, 6]. In this scheme a fixed state is taken as the blank state, depending on which and the initial machine state, the cloning operation is constructed. We extend this operation such that any arbitrary (pure or mixed) state taken as the blank copy can do the job. The optimal universal 1 → 2 inexact qubit cloner of Brußet al.[5] takes an arbitrary qubit |ψ 〉 〈ψ | = 1 2 (I + − → s. − → σ) along with a fixed blank qubit |b 〉 and a machine state |M 〉 as input. An entangled state of the three qubits is produced as the output such that the reduced density matrices of the first two qubits are two similar approximate copies ρ = 1 2 (I + η− → s. − → σ) of |ψ 〉 〈ψ | with η = 2 3. The unitary operator realizing this process is defined on the combined Hilbert space of the input qubit, the blank qubit and machine by U ′ √ √

•Jan 1, 2001•1 citation

Scheme for Implementing Quantum Cloning Restoring Machine in Cavity QED

Long-Bao Yu, Wen‐Hai Zhang, Ye Liu

We propose an experimentally feasible scheme for implementing quantum restoring machine of the optimal universal 1→2 quantum cloning machine in the context of cavity QED. In our scheme, two atoms (the clones) simultaneously interact with a cavity field, and meanwhile they are driven by a classical field. Then an arbitrary unknown input state can be restored in the ancilla by applying appropriate unitary local operation.

Communications in Theoretical Physics•Feb 1, 2007•2 citations

Optimal partial deterministic quantum teleportation of qubits

Ladislav Mišta, Radim Filip

We propose a protocol implementing optimal partial deterministic quantum teleportation for qubits. This is a teleportation scheme realizing deterministically an optimal $1\ensuremath{\rightarrow}2$ asymmetric universal cloning where one imperfect copy of the input state emerges at the sender's station while the other copy emerges at receiver's possibly distant station. The optimality means that the fidelities of the copies saturate the asymmetric cloning inequality. The performance of the protocol relies on the partial deterministic nondemolition Bell measurement that allows us to continuously control the flow of information among the outgoing qubits. We also demonstrate that the measurement is optimal two-qubit operation in the sense of the trade-off between the state disturbance and the information gain.

Physical Review A•Feb 24, 2005•9 citations

Manipulating quantum information via quantum cloning

F. De Martini, L. Masullo, Marco Ricci +2 more

An extensive characterization of the information flux underlying the 1 → 2 universal cloning process is presented together with the realization of several cloning and measurement tasks.The restoration of both the quantum and classical information associated to the input qubit was theoretically analysed and experimentally accomplished.At the same time the extension of the 1 → 2 cloning to the 1 → 3 universal and covariant processes is reported with the first experimental optical realizations.

Journal of Optics B Quantum and Semiclassical Optics•Nov 22, 2005•1 citation
We study measurements on various subsystems of the output of a universal 1\ensuremath→2\stackrel{\ensuremath{\rightarrow}}{1}21\ensuremath→​2 cloning machine, and establish a correspondence between these measurements at the output and effective measurements on the original input. We show that one can implement sharp effective measurement elements by measuring only two out of the three output systems. Additionally, certain complete sets of sharp measurements on the input can be realized by measurements on the two clones. Furthermore, we introduce a scheme that allows us to restore the original input in one of the output bits, by using measurements and classical communication---a protocol that resembles teleportation.
The quantum cloner machine maps an unknown arbitrary input qubit into two optimal clones and one optimal flipped qubit. By combining linear and nonlinear optical methods we experimentally implement a scheme that, after the cloning transformation, restores the original input qubit in one of the output channels, by using local measurements, classical communication, and feedforward. This nonlocal method demonstrates how the information on the input qubit can be restored after the cloning process. The realization of the reversion process is expected to find useful applications in the field of modern multipartite quantum cryptography.
Abstract We investigate prepare-and-measure scenarios in which a sender and a receiver use entanglement to send quantum information over a channel with limited capacity. We formalise this framework, identify its basic properties and provide numerical tools for optimising quantum protocols for generic communication tasks. The seminal protocol for sending quantum information over a classical channel is teleportation. We study a natural stochastic generalisation in which the sender holds N qubits from which the receiver can recover one on demand. We show that, if the classical communication is allowed to exploit extremal non-signalling correlations, then two bits of communication suffice to solve this task exactly for any N . We then consider entanglement-based protocols and show that these can be constructed systematically by leveraging connections to several well-known quantum information primitives, such as teleportation, cloning machines and random access coding. In particular, we show that by using genuine multi-particle entangled measurements, one can construct a universal stochastic teleportation machine, i.e. a device whose teleportation fidelity is independent of the quantum input.
We show that using a fixed cloning machine, whether deterministic inexact or probabilistic exact, one can take an arbitrary blank state. Quantum information cannot be cloned. There cannot exist a machine which can produce two (or more) exact copies of an arbitrary state in a deterministic manner [1]. Replication is not allowed even when the input state is taken at random from a given set of two non-orthogonal states [2]. It has been further shown that probabilistic cloning is not possible if the input state is from a given linearly dependent set [3]. Henceforth we deal explicitly with qubits although all the results can be extended to higher dimensions. Although exact cloning is not possible, one can approximately clone an arbitrary input state [4, 5, 6]. In this scheme a fixed state is taken as the blank state, depending on which and the initial machine state, the cloning operation is constructed. We extend this operation such that any arbitrary (pure or mixed) state taken as the blank copy can do the job. The optimal universal 1 → 2 inexact qubit cloner of Brußet al.[5] takes an arbitrary qubit |ψ 〉 〈ψ | = 1 2 (I + − → s. − → σ) along with a fixed blank qubit |b 〉 and a machine state |M 〉 as input. An entangled state of the three qubits is produced as the output such that the reduced density matrices of the first two qubits are two similar approximate copies ρ = 1 2 (I + η− → s. − → σ) of |ψ 〉 〈ψ | with η = 2 3. The unitary operator realizing this process is defined on the combined Hilbert space of the input qubit, the blank qubit and machine by U ′ √ √
We propose a protocol implementing optimal partial deterministic quantum teleportation for qubits. This is a teleportation scheme realizing deterministically an optimal $1\ensuremath{\rightarrow}2$ asymmetric universal cloning where one imperfect copy of the input state emerges at the sender's station while the other copy emerges at receiver's possibly distant station. The optimality means that the fidelities of the copies saturate the asymmetric cloning inequality. The performance of the protocol relies on the partial deterministic nondemolition Bell measurement that allows us to continuously control the flow of information among the outgoing qubits. We also demonstrate that the measurement is optimal two-qubit operation in the sense of the trade-off between the state disturbance and the information gain.
An extensive characterization of the information flux underlying the 1 → 2 universal cloning process is presented together with the realization of several cloning and measurement tasks.The restoration of both the quantum and classical information associated to the input qubit was theoretically analysed and experimentally accomplished.At the same time the extension of the 1 → 2 cloning to the 1 → 3 universal and covariant processes is reported with the first experimental optical realizations.