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We propose an interferometric scheme for the estimation of a linear combination with non-negative weights of an arbitrary number $M>1$ of unknown phase delays, distributed across an $M$-channel linear optical network, with…

Quantum Physics · Physics 2019-12-04 Dario Gatto , Paolo Facchi , Frank Narducci , Vincenzo Tamma

The router is a key element for a network. We describe a scheme to realize genuine quantum routing of single-photon pulses based on cascading of conditional quantum gates in a Mach-Zehnder interferometer and report a proof-of-principle…

Quantum Physics · Physics 2015-08-10 X. X. Yuan , J. -J. Ma , P. -Y. Hou , X. -Y. Chang , C. Zu , L. -M. Duan

Classical communication schemes that exploit wave modulation are the basis of the information era. The transfer of information based on the quantum properties of photons revolutionized these modern communication techniques. Here we…

Quantum Physics · Physics 2020-08-31 Robin Röpke , Nicole Kerker , Alexander Stibor

We theoretically propose a multiparameter cascaded quantum interferometer in which a two-input and two-output setup is obtained by concatenating 50:50 beam splitters with $n$ independent and adjustable time delays. A general method for…

Quantum Physics · Physics 2024-11-19 Baihong Li , Qi-qi Li , Zhuo-zhuo Wang , Penglong Wang , Changhua Chen , Boxin Yuan , Yiwei Zhai , Xiaofei Zhang

Achieving the ultimate quantum precision in the estimation of multiple physical parameters simultaneously is a challenge in quantum metrology due to fundamental limitations and experimental challenges in harnessing the necessary quantum…

Quantum Physics · Physics 2025-06-24 Atmadev Rai , Danilo Triggiani , Paolo Facchi , Vincenzo Tamma

The quantum superposition principle implies that a particle entering an interferometer evolves by simultaneously taking both arms. If a non-destructive, minimally-disturbing interaction coupling a particle property to a pointer is…

We propose an alignment-free two-party polarization-entanglement transmission scheme for entangled photons by using only linear-optical elements, requiring neither ancillary photons nor calibrated reference frames. The scheme is robust…

Quantum Physics · Physics 2020-01-08 Peng-Liang Guo , Tao Li , Qing Ai , Fu-Guo Deng

The criticism of the experiment showing disconnected traces of photons passing through a nested Mach-Zehnder interferometer is shown to be unfounded.

Quantum Physics · Physics 2017-03-13 Lev Vaidman

Quantum secure direct communications (QSDC) can directly transmit secret messages through a quantum channel without keys. The imperfect photon source is a major obstacle for QSDC's practical implementation. The unwanted vacuum state and…

Quantum Physics · Physics 2024-08-21 Jia-Wei Ying , Peng Zhao , Wei Zhong , Ming-Ming Du , Xi-Yun Li , Shu-Ting Shen , An-Lei Zhang , Lan Zhou , Yu-Bo Sheng

Based on the ideal of order rearrangement and block transmission of photons, we present a quantum secure direct communication scheme using single photons. The security of the present scheme is ensured by quantum no-cloning theory and the…

Quantum Physics · Physics 2009-11-13 Jian Wang , Quan Zhang , Chao-jing Tang

Quantum secure direct communication (QSDC) is the technology to transmit secret information directly through a quantum channel without neither key nor ciphertext. It provides us with a secure communication structure that is fundamentally…

Quantum Physics · Physics 2018-05-21 Zeng-Rong Zhou , Yu-Bo Sheng , Peng-Hao Niu , Liu-Guo Yin , Gui-Lu Long

We demonstrate Mach-Zehnder-type interferometry in a superconducting flux qubit. The qubit is a tunable artificial atom, whose ground and excited states exhibit an avoided crossing. Strongly driving the qubit with harmonic excitation sweeps…

Decoherence is detrimental to quantum key distribution (QKD) over large distances. One of the proposed solutions is to use quantum repeaters, which divide the total distance between the users into smaller segments to minimise the effects of…

Two photons in free space pass each other undisturbed. This is ideal for the faithful transmission of information, but prohibits an interaction between the photons as required for a plethora of applications in optical quantum information…

Quantum Physics · Physics 2017-02-17 Bastian Hacker , Stephan Welte , Gerhard Rempe , Stephan Ritter

Nowadays, quantum router is playing a key role in quantum communication and quantum network- s. Here we propose a tunable single-photon routing scheme, based on quantum interference, which uses two distant artificial atoms coupling to two…

Quantum Physics · Physics 2016-04-20 Xin-Yu Chen , Feng-Yang Zhang , Chong Li

Photons are the ideal carriers of quantum information for communication. Each photon can have a single qubit or even multiple qubits encoded in its internal quantum state, as defined by optical degrees of freedom such as polarization,…

In an recent work with the title "Asking Photons Where They Have Been", Danan et al. experimentally demonstrate an intriguing behavior of photons in an interferometer [Phys. Rev. Lett. 111, 240402 (2013)]. In their words: "The photons tell…

Quantum Physics · Physics 2014-03-14 Pablo L. Saldanha

We provide the first example of a communication model and a distributed task, for which there exists a realistic quantum protocol which is asymptotically more efficient than any classical protocol, both in the communication and the…

Quantum Physics · Physics 2017-04-05 Niraj Kumar , Eleni Diamanti , Iordanis Kerenidis

Multi-photon propagation in connected structures - a quantum walk - offers the potential for simulating complex physical systems and provides a route to universal quantum computation. Increasing the complexity of quantum photonic networks…

Quantum Physics · Physics 2016-03-21 Hugo Defienne , Marco Barbieri , Ian A. Walmsley , Brian J. Smith , Sylvain Gigan

Quantum digital signature (QDS) is the quantum version of its classical counterpart, and can offer security against attacks of repudiation, signature forging and external eavesdropping, on the basis of quantum mechanical no-go principles.…

Quantum Physics · Physics 2024-06-21 Vinod N. Rao , Shrikant Utagi , Anirban Pathak , R. Srikanth