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The concept of mode locking in laser is applied to a two-photon state with frequency entanglement. Cavity enhanced parametric down-conversion is found to produce exactly such a state. The mode-locked two-photon state exhibits a comb-like…

Quantum Physics · Physics 2009-11-10 Y. J. Lu , R. L. Campbell , Z. Y. Ou

Photonic time-frequency entanglement is a promising resource for quantum information processing technologies. We investigate swapping of continuous-variable entanglement in the time-frequency degree of freedom using three-wave mixing in the…

We study a possibility of measuring the time-resolved second-order autocorrelation function of one of two beams generated in type-II parametric downconversion by means of temporal magnification of this beam, bringing its correlation time…

Path-entangled N-photon states can be obtained through the coalescence of indistinguishable photons inside linear networks. They are key resources for quantum enhanced metrology, quantum imaging, as well as quantum computation based on…

Biphoton systems exhibiting entanglement in position-momentum variables, known as spatial entanglement, are among the most intriguing and well-studied phenomena in quantum optics. A notable subset of these are phase entangled states, where…

Quantum Physics · Physics 2025-08-26 Rounak Chatterjee , Mayuresh Kanagal , Vikas S Bhat , Kiran Bajar , Sushil Mujumdar

Accurately establishing the state of large-scale quantum systems is an important tool in quantum information science; however, the large number of unknown parameters hinders the rapid characterisation of such states, and reconstruction…

Quantum Physics · Physics 2014-07-30 Francesco Tonolini , Susan Chan , Megan Agnew , Alan Lindsay , Jonathan Leach

Precise measurements are the key to advances in all fields of science. Quantum entanglement shows higher sensitivity than achievable by classical methods. Most physical quantities including position, displacement, distance, angle, and…

Quantum Physics · Physics 2017-07-05 Zhi-Yuan Zhou , Shi-Long Liu , Shi-Kai Liu , Yin-Hai Li , Dong-Sheng Ding , Guang-Can Guo , Bao-Sen Shi

We demonstrate a new class of frequency-entangled states generated via spontaneous parametric down-conversion under extended phase matching conditions. Biphoton entanglement with coincident signal and idler frequencies is observed over a…

Quantum Physics · Physics 2009-11-10 Onur Kuzucu , Marco Fiorentino , Marius A. Albota , Franco N. C. Wong , Franz X. Kaertner

We experimentally demonstrate shaping of the two-photon wavefunction of entangled photon-pairs, utilizing coherent pulse-shaping techniques. By performing spectral-phase manipulations we tailor the two-photon wavefunction exactly like a…

Quantum Physics · Physics 2011-12-06 Avi pe'er , Barak Dayan , Asher A. Friesem , Yaron Silberberg

Using a spontaneous parametric-downconversion source of photon pairs, we are working towards the creation of arbitrary 2-qubit quantum states with high fidelity. Currently, all physically allowable combinations of polarization entanglement…

Quantum Physics · Physics 2007-05-23 Paul Kwiat , Joe Altepeter , David Branning , Evan Jeffrey , Nicholas Peters , Tzu-Chieh Wei

The resources needed to conventionally characterize a quantum system are overwhelmingly large for high- dimensional systems. This obstacle may be overcome by abandoning traditional cornerstones of quantum measurement, such as general…

Quantum Physics · Physics 2016-05-17 Gregory A. Howland , Samuel H. Knarr , James Schneeloch , Daniel J. Lum , John C. Howell

We implement a double-pixel, compressive sensing camera to efficiently characterize, at high resolution, the spatially entangled fields produced by spontaneous parametric downconversion. This technique leverages sparsity in spatial…

Quantum Physics · Physics 2013-02-25 Gregory A. Howland , John C. Howell

Verifying entanglement with experimental measurements requires that we take the limitations of experimental techniques into account, while still proving that the data obtained could not have been generated from a classical source. In the…

Frequency-bin entangled photons can be efficiently produced on-chip which offers a scalable, robust and low-footprint platform for quantum communication, particularly well-suited for resource-constrained settings such as mobile or…

The large capacity and robustness of information encoding in the temporal mode of photons is important in quantum information processing, in which characterizing temporal quantum states with high usability and time resolution is essential.…

The measurement of the position-momentum EPR correlations of a two-photon state is important for many quantum information applications ranging from quantum key distribution to coincidence imaging. However, all the existing techniques for…

Quantum Physics · Physics 2022-09-28 Abhinandan Bhattacharjee , Nilakantha Meher , Anand K. Jha

The certificate of success for a number of important quantum information processing protocols, such as entanglement distillation, is based on the difference in the entanglement content of the quantum states before and after the protocol. In…

Quantum Physics · Physics 2015-05-14 G. Puentes , A. Datta , A. Feito , J. Eisert , M. B. Plenio , I. A. Walmsley

Precision measurements of optical phases have many applications in science and technology. Entangled multi-photon states have been suggested for performing such measurements with precision that significantly surpasses the shot-noise limit.…

Mesoscale and Nanoscale Physics · Physics 2020-07-01 Giora Peniakov , Zu-En Su , Ayal Beck , Dan Cogan , Or Amar , David Gershoni

Entangled photons have the remarkable ability to be more sensitive to signal and less sensitive to noise than classical light. Joint photons can sample an object collectively, resulting in faster phase accumulation and higher spatial…

Optics · Physics 2015-09-04 Chien-Hung Lu , Matthew Reichert , Xiaohang Sun , Jason W. Fleischer

The reconstruction of density matrices from measurement data (quantum state tomography) is the most comprehensive method for assessing the accuracy and performance of quantum devices. Existing methods to reconstruct two-photon density…

Quantum Physics · Physics 2025-03-12 Salini Rajeev , Mayukh Lahiri