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:1111.7283 · Physical Review Letters

Proposal for Inverting the Quantum Cloning of Photons

Sadegh Raeisi, Wolfgang Tittel, Christoph Simon

Published Mar 22, 2012• 18 citations
arXivHTMLPDF

Abstract

We propose an experiment where a photon is first cloned by stimulated parametric down-conversion, making many (imperfect) copies, and then the cloning transformation is inverted, regenerating the original photon while destroying the copies. Focusing on the case where the initial photon is entangled with another photon, we study the conditions under which entanglement can be proven in the final state. The proposed experiment would provide a clear demonstration that quantum information is preserved in quantum cloning. It would furthermore allow a definitive experimental proof for micro-macro entanglement in the intermediate multiphoton state, which is still an outstanding challenge. Finally, it might provide a quantum detection technique for small differences in transmission (e.g., in biological samples), whose sensitivity scales better with the number of photons used than a classical transmission measurement.

DOI
10.1103/physrevlett.108.120404

Related papers

Experimental Quantum Cloning of Single Photons

Antı́a Lamas-Linares, Christoph Simon, John C. Howell +1 more

Although perfect copying of unknown quantum systems is forbidden by the laws of quantum mechanics, approximate cloning is possible. A natural way of realizing quantum cloning of photons is by stimulated emission. In this context, the fundamental quantum limit to the quality of the clones is imposed by the unavoidable presence of spontaneous emission. In our experiment, a single input photon stimulates the emission of additional photons from a source on the basis of parametric down-conversion. This leads to the production of quantum clones with near-optimal fidelity. We also demonstrate universality of the copying procedure by showing that the same fidelity is achieved for arbitrary input states.

arXiv:quant-ph/0205149•Science•Apr 26, 2002•278 citations

Path entangled photons from parametric down-conversion

H. S. Eisenberg, Juan F. Hodelin, G. Khoury +1 more

Using stimulated parametric down-conversion, we propose a method for generating multiphoton path entanglement. By a special coincidence detection at one down-converted arm, the photons of the second arm non-locally bunch into the desired state. Experimental demonstration for the case of two photons is presented, as well as how to extend the scheme to any number of photons.

Quantum Electronics and Laser Science Conference•Dec 10, 2005•0 citations

Path Entangled Photons from Parametric Down-Conversion

H. S. Eisenberg, Juan F. Hodelin, G. Khoury +1 more

Using stimulated parametric down-conversion, we propose a method for generating multiphoton path entanglement. By a special coincidence detection at one down-converted arm, the photons of the second arm non-locally bunch into the desired state. Experimental demonstration for the case of two photons is presented, as well as how to extend the scheme to any number of photons.

Bulletin of the American Physical Society•Mar 24, 2005•0 citations

Towards Quantum Experiments with Human Eyes as Detectors Based on Cloning via Stimulated Emission

Pavel Sekatski, Nicolas Brunner, Cyril Branciard +2 more

We show theoretically that a large Bell inequality violation can be obtained with human eyes as detectors, in a "micro-macro" experiment where one photon from an entangled pair is greatly amplified via stimulated emission. The violation is robust under photon loss. This leads to an apparent paradox, which we resolve by noting that the violation proves the existence of entanglement before the amplification. The same is true for the micro-macro experiments performed so far with conventional detectors. However, we also prove that there is genuine micro-macro entanglement even for high loss.

arXiv:0902.2896•Physical Review Letters•Sep 8, 2009•76 citations

Knowing and not knowing : obtaining quantum information advantages with photons

Dominick J. Joch

The photon is a quantum system that is by nature robust against noise, and fast travelling, providing an ideal information carrier for quantum information science. The field of quantum information science has generated a great deal of interest for both researchers and the public due to the advantages it can have over classical technologies in areas including communication, computing and cryptography. In this thesis, I explore several different ways that photons can be used to realize quantum information advantages and enable quantum technologies, information tasks and fundamental studies of physics. A strong emphasis is placed on their practical implementation in optical experiments, where the challenges of noise, loss and device imperfections must be considered and combated. I utilize spontaneous parametric downconversion-based sources of high-quality single photons, and their polarization, path, and temporal degrees of freedom for encoding quantum information. In my first experimental project, I demonstrate the first violation of noncontextuality with time-polarization intraparticle entangled states encoded in a single photon by implementing a powerful interference-based measurement technique for photonic states. I perform a test of noncontextuality, acquiring a parameter |SCHSH| = 2.744 ± 0.006, which violates the classical bound of 2 by over 110 standard deviations, rigorously certifying both entanglement and contextuality of the system. We propose a new approach for preparing and measuring high-dimensional time-bin states, that overcomes many of the limitations of previous techniques, and demonstrate it for time-bin qubits and qutrits. In the next experimental project, I investigate the topic of universal cloning in quantum steering-with cloning and steering being two fundamental aspects of quantum physics deeply involved in the security of quantum protocols. I report the first experimental demonstration of cloned quantum steering, showing a simultaneous violation in a steering test by two clones made from one part of an entangled pair of photons. This provides a conclusive result on the question of whether the cloning of quantum steering is possible. We also present theoretical results that clarify our understanding of cloned steering for qubits: we find a no-go theorem where quantum steering can only be copied by a qubit universal cloning machine for 2 and 3 clones, and a monogamy relation where for N clones, steering is only possible if a minimum of N + 1 measurements are performed on each clone. I discuss the field of random number generation, and study how quantum physics allows for certifiably unpredictable random sequences, without needing complete trust in all of the physical devices, offering high levels of security over classical approaches. I report the first discrete-variable detection-loophole-free implementation of one-sided device-independent randomness expansion of certified random bits, based on the quantum steering task. These results illustrate an approach to secure randomness with greater tolerance to noise and loss compared to Bell test-based protocols. The final experimental project looks at quantum autoencoders, which are a quantum machine learning tool that we investigate for the purpose of denoising quantum states. I model and simulate a denoising quantum autoencoder which compresses ququarts into a qubit space and reconstructs noise-reduced ququart states. I construct an experimental apparatus that implements this device, and demonstrate quantum state tomography of ququart states, and the training of the autoencoder.

•Jul 3, 2025•0 citations

Cloning entangled photons to scales one can see

Pavel Sekatski, Bruno Sanguinetti, Enrico Pomarico +2 more

By amplifying photonic qubits it is possible to produce states that contain enough photons to be seen with the human eye, potentially bringing quantum effects to macroscopic scales [P. Sekatski, N. Brunner, C. Branciard, N. Gisin, and C. Simon, Phys. Rev. Lett. 103, 113601 (2009)]. In this paper we theoretically study quantum states obtained by amplifying one side of an entangled photon pair with different types of optical cloning machines for photonic qubits. We propose a detection scheme that involves lossy threshold detectors (such as the human eye) on the amplified side and conventional photon detectors on the other side. We show that correlations obtained with such coarse-grained measurements prove the entanglement of the initial photon pair and do not prove the entanglement of the amplified state. We emphasize the importance of the detection loophole in Bell violation experiments by giving a simple preparation technique for separable states that violate a Bell inequality without closing this loophole. Finally, we analyze the genuine entanglement of the amplified states and its robustness to losses before, during, and after amplification.

arXiv:1005.5083•Physical Review A•Nov 15, 2010•45 citations
We propose an experiment where a photon is first cloned by stimulated parametric down-conversion, making many (imperfect) copies, and then the cloning transformation is inverted, regenerating the original photon while destroying the copies. Focusing on the case where the initial photon is entangled with another photon, we study the conditions under which entanglement can be proven in the final state. The proposed experiment would provide a clear demonstration that quantum information is preserved in quantum cloning. It would furthermore allow a definitive experimental proof for micro-macro entanglement in the intermediate multiphoton state, which is still an outstanding challenge. Finally, it might provide a quantum detection technique for small differences in transmission (e.g., in biological samples), whose sensitivity scales better with the number of photons used than a classical transmission measurement.
Although perfect copying of unknown quantum systems is forbidden by the laws of quantum mechanics, approximate cloning is possible. A natural way of realizing quantum cloning of photons is by stimulated emission. In this context, the fundamental quantum limit to the quality of the clones is imposed by the unavoidable presence of spontaneous emission. In our experiment, a single input photon stimulates the emission of additional photons from a source on the basis of parametric down-conversion. This leads to the production of quantum clones with near-optimal fidelity. We also demonstrate universality of the copying procedure by showing that the same fidelity is achieved for arbitrary input states.
We show theoretically that a large Bell inequality violation can be obtained with human eyes as detectors, in a "micro-macro" experiment where one photon from an entangled pair is greatly amplified via stimulated emission. The violation is robust under photon loss. This leads to an apparent paradox, which we resolve by noting that the violation proves the existence of entanglement before the amplification. The same is true for the micro-macro experiments performed so far with conventional detectors. However, we also prove that there is genuine micro-macro entanglement even for high loss.
The photon is a quantum system that is by nature robust against noise, and fast travelling, providing an ideal information carrier for quantum information science. The field of quantum information science has generated a great deal of interest for both researchers and the public due to the advantages it can have over classical technologies in areas including communication, computing and cryptography. In this thesis, I explore several different ways that photons can be used to realize quantum information advantages and enable quantum technologies, information tasks and fundamental studies of physics. A strong emphasis is placed on their practical implementation in optical experiments, where the challenges of noise, loss and device imperfections must be considered and combated. I utilize spontaneous parametric downconversion-based sources of high-quality single photons, and their polarization, path, and temporal degrees of freedom for encoding quantum information. In my first experimental project, I demonstrate the first violation of noncontextuality with time-polarization intraparticle entangled states encoded in a single photon by implementing a powerful interference-based measurement technique for photonic states. I perform a test of noncontextuality, acquiring a parameter |SCHSH| = 2.744 ± 0.006, which violates the classical bound of 2 by over 110 standard deviations, rigorously certifying both entanglement and contextuality of the system. We propose a new approach for preparing and measuring high-dimensional time-bin states, that overcomes many of the limitations of previous techniques, and demonstrate it for time-bin qubits and qutrits. In the next experimental project, I investigate the topic of universal cloning in quantum steering-with cloning and steering being two fundamental aspects of quantum physics deeply involved in the security of quantum protocols. I report the first experimental demonstration of cloned quantum steering, showing a simultaneous violation in a steering test by two clones made from one part of an entangled pair of photons. This provides a conclusive result on the question of whether the cloning of quantum steering is possible. We also present theoretical results that clarify our understanding of cloned steering for qubits: we find a no-go theorem where quantum steering can only be copied by a qubit universal cloning machine for 2 and 3 clones, and a monogamy relation where for N clones, steering is only possible if a minimum of N + 1 measurements are performed on each clone. I discuss the field of random number generation, and study how quantum physics allows for certifiably unpredictable random sequences, without needing complete trust in all of the physical devices, offering high levels of security over classical approaches. I report the first discrete-variable detection-loophole-free implementation of one-sided device-independent randomness expansion of certified random bits, based on the quantum steering task. These results illustrate an approach to secure randomness with greater tolerance to noise and loss compared to Bell test-based protocols. The final experimental project looks at quantum autoencoders, which are a quantum machine learning tool that we investigate for the purpose of denoising quantum states. I model and simulate a denoising quantum autoencoder which compresses ququarts into a qubit space and reconstructs noise-reduced ququart states. I construct an experimental apparatus that implements this device, and demonstrate quantum state tomography of ququart states, and the training of the autoencoder.
By amplifying photonic qubits it is possible to produce states that contain enough photons to be seen with the human eye, potentially bringing quantum effects to macroscopic scales [P. Sekatski, N. Brunner, C. Branciard, N. Gisin, and C. Simon, Phys. Rev. Lett. 103, 113601 (2009)]. In this paper we theoretically study quantum states obtained by amplifying one side of an entangled photon pair with different types of optical cloning machines for photonic qubits. We propose a detection scheme that involves lossy threshold detectors (such as the human eye) on the amplified side and conventional photon detectors on the other side. We show that correlations obtained with such coarse-grained measurements prove the entanglement of the initial photon pair and do not prove the entanglement of the amplified state. We emphasize the importance of the detection loophole in Bell violation experiments by giving a simple preparation technique for separable states that violate a Bell inequality without closing this loophole. Finally, we analyze the genuine entanglement of the amplified states and its robustness to losses before, during, and after amplification.