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We study quantum process tomography given the prior information that the map is a unitary or close to a unitary process. We show that a unitary map on a $d$-level system is completely characterized by a minimal set of $d^2{+}d$ elements…

Quantum Physics · Physics 2014-07-23 Charles H. Baldwin , Amir Kalev , Ivan H. Deutsch

Complete characterization of a multimode optical process has paved the way for understanding complex optical phenomena, leading to the development of novel optical technologies. Until now, however, characterizations have mainly focused on a…

Quantum Physics · Physics 2026-05-13 Geunhee Gwak , Chan Roh , Young-Do Yoon , M. S. Kim , Young-Sik Ra

A fundamental element of quantum information processing with photonic qubits is the nonclassical quantum interference between two photons when they bunch together via the Hong-Ou-Mandel (HOM) effect. Ultimately, many such pure photons must…

We significantly extend recently developed methods to faithfully reconstruct unknown quantum states that are approximately low-rank, using only a few measurement settings. Our new method is general enough to allow for measurements from a…

Quantum Physics · Physics 2012-07-11 Matthias Ohliger , Vincent Nesme , David Gross , Yi-Kai Liu , Jens Eisert

An optical waveplate rotating light polarization can be modeled as a single-qubit unitary operator, whose action can be experimentally determined via quantum process tomography. Standard approaches to tomographic problems rely on the…

In this paper we describe in detail and generalize a method for quantum process tomography that was presented in [A. Bendersky, F. Pastawski, J. P. Paz, Physical Review Letters 100, 190403 (2008)]. The method enables the efficient…

Quantum Physics · Physics 2015-05-13 Ariel Bendersky , Fernando Pastawski , Juan Pablo Paz

Entangled measurement is a crucial tool in quantum technology. We propose a new entanglement measure of multi-mode detection, which estimates the amount of entanglement that can be created in a measurement. To illustrate the proposed…

We present a method for spatially resolved multiphoton counting based on an intensified camera with the retrieval of multimode photon statistics fully accounting for non-linearities in the detection process. The scheme relies on one-time…

Quantum Physics · Physics 2015-08-04 Radoslaw Chrapkiewicz , Wojciech Wasilewski , Konrad Banaszek

Hong-Ou-Mandel (HOM) interference is a compelling quantum phenomenon that demonstrates the nonclassical nature of single photons. In this study, we investigate an electromagnetically induced transparency-based double-$\Lambda$ four-wave…

Quantum Physics · Physics 2023-07-19 Zi-Yu Liu , Jiun-Shiuan Shiu , Chin-Yao Cheng , Yong-Fan Chen

Displaced Fock states of the electromagnetic field have been synthesized by overlapping the pulsed optical single-photon Fock state |1> with coherent states on a high-reflection beamsplitter and completely characterized by means of quantum…

Quantum Physics · Physics 2009-11-07 A. I. Lvovsky , S. A. Babichev

The Hong-Ou-Mandel (HOM) effect ranks among the most notable quantum interference phenomena, and is central to many applications in quantum technologies. The fundamental effect appears when two independent and indistinguishable photons are…

The data-embedding process is one of the bottlenecks of quantum machine learning, potentially negating any quantum speedups. In light of this, more effective data-encoding strategies are necessary. We propose a photonic-based bosonic…

Quantum Physics · Physics 2022-06-24 Beng Yee Gan , Daniel Leykam , Dimitris G. Angelakis

We introduce a method of quantum tomography for a continuous variable system in position and momentum space. We consider a single two-level probe interacting with a quantum harmonic oscillator by means of a class of Hamiltonians, linear in…

Quantum Physics · Physics 2015-03-19 J. Casanova , C. E. Lopez , J. J. Garcia-Ripoll , C. F. Roos , E. Solano

Using a continuous-wave type-II optical parametric oscillator below threshold, we have demonstrated a novel source of heralded single-photons with high-fidelity. The generated state is characterized by homodyne detection and exhibits a 79%…

Quantum Physics · Physics 2012-10-11 Olivier Morin , Virginia D'Auria , Claude Fabre , Julien Laurat

We demonstrate a novel experimental technique for quantum-state tomography of the collective density matrix. It is based on measurements of the polarization of light, traversing the atomic vapor. To assess the technique's robustness against…

Quantum Physics · Physics 2025-08-29 Marek Kopciuch , Magdalena Smolis , Adam Miranowicz , Szymon Pustelny

The characterization of a unitary gate is experimentally accomplished via Quantum Process Tomography, which combines the outcomes of different projective measurements to reconstruct the underlying operator. The process matrix is typically…

Quantum Physics · Physics 2025-09-17 Tareq Jaouni , Francesco Di Colandrea , Lorenzo Amato , Filippo Cardano , Ebrahim Karimi

Wigner function tomography is indispensable for characterizing quantum states, but its commonly used version, balanced homodyne detection, suffers from several weaknesses. First, it requires efficient detection, which is critical for…

Quantum Physics · Physics 2023-08-25 Mahmoud Kalash , Maria V. Chekhova

We present a novel method for quantum tomography of multi-qubit states. We apply the method to spin-multi-photon states, which we produce by periodic excitation of a semiconductor quantum-dot- confined spin every 1/4 of its coherent…

Quantum Physics · Physics 2021-08-16 Dan Cogan , Giora Peniakov , Oded Kenneth , Yaroslav Don , David Gershoni

We suggest and demonstrate a scheme to reconstruct the symmetric two-mode squeezed thermal states of spectral sideband modes from an optical parametric oscillator. The method is based on a single homodyne detector and active stabilization…

Quantum Physics · Physics 2016-04-13 Simone Cialdi , Carmen Porto , Daniele Cipriani , Stefano Olivares , Matteo G. A. Paris

When two indistinguishable bosons interfere at a beam splitter, they both exit through the same output port. This foundational quantum-mechanical phenomenon, known as the Hong-Ou-Mandel (HOM) effect, has become a cornerstone in the field of…

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