scholarly journals Efficient production of large-size optical Schrödinger cat states

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Evgeny V. Mikheev ◽  
Alexander S. Pugin ◽  
Dmitry A. Kuts ◽  
Sergey A. Podoshvedov ◽  
Nguyen Ba An
Keyword(s):  
Quantum Information Processing ◽  
Photon Number ◽  
Analytical Form ◽  
Entangled State ◽  
Efficient Production ◽  
Large Size ◽  
Novel Theory ◽  
Laser Sources ◽  
Schrödinger Cat ◽  
Cat States

Abstract We present novel theory of effective realization of large-size optical Schrödinger cat states, which play an important role for quantum communication and quantum computation in the optical domain using laser sources. The treatment is based on the α-representation in infinite Hilbert space which is the decomposition of an arbitrary quantum state in terms of displaced number states characterized by the displacement amplitude α. We find analytical form of the α-representation for both even and odd Schrödinger cat states which is essential for their generation schemes. Two schemes are proposed for generating even/odd Schrödinger cat states of large size |β| (|β| ≥ 2) with high fidelity F (F ≈ 0.99). One scheme relies on an initially offline prepared two-mode entangled state with a fixed total photon number, while the other scheme uses separable photon Fock states as the input. In both schemes, generation of the desired states is heralded by the corresponding measurement outcomes. Conditions for obtaining states useful for quantum information processing are established and success probabilities for their generation are evaluated.

scholarly journals Generation of multicomponent atomic Schrödinger cat states of up to 20 qubits

Science ◽  
2019 ◽  
Vol 365 (6453) ◽  
pp. 574-577 ◽  
Author(s):  
Chao Song ◽  
Kai Xu ◽  
Hekang Li ◽  
Yu-Ran Zhang ◽  
Xu Zhang ◽  
...  
Keyword(s):  
Quantum Information ◽  
Information Science ◽  
Quantum Information Processing ◽  
Ghz State ◽  
Many Body ◽  
Time Intervals ◽  
Fundamental Physics ◽  
Schrödinger Cat ◽  
Many Body Systems ◽  
Cat States

Multipartite entangled states are crucial for numerous applications in quantum information science. However, the generation and verification of multipartite entanglement on fully controllable and scalable quantum platforms remains an outstanding challenge. We report the deterministic generation of an 18-qubit Greenberger-Horne-Zeilinger (GHZ) state and multicomponent atomic Schrödinger cat states of up to 20 qubits on a quantum processor, which features 20 superconducting qubits, also referred to as artificial atoms, interconnected by a bus resonator. By engineering a one-axis twisting Hamiltonian, the system of qubits, once initialized, coherently evolves to multicomponent atomic Schrödinger cat states—that is, superpositions of atomic coherent states including the GHZ state—at specific time intervals as expected. Our approach on a solid-state platform should not only stimulate interest in exploring the fundamental physics of quantum many-body systems, but also enable the development of applications in practical quantum metrology and quantum information processing.

scholarly journals Engineering Schrödinger cat states with a photonic even-parity detector

Quantum ◽  
2020 ◽  
Vol 4 ◽  
pp. 239 ◽  
Author(s):  
G. S. Thekkadath ◽  
B. A. Bell ◽  
I. A. Walmsley ◽  
A. I. Lvovsky
Keyword(s):  
Time Reversal ◽  
Coherent States ◽  
Beam Splitter ◽  
Photon Number ◽  
Input State ◽  
Interference Phenomenon ◽  
Arbitrary Size ◽  
Two Component ◽  
Schrödinger Cat ◽  
Cat States

When two equal photon-number states are combined on a balanced beam splitter, both output ports of the beam splitter contain only even numbers of photons. Consider the time-reversal of this interference phenomenon: the probability that a pair of photon-number-resolving detectors at the output ports of a beam splitter both detect the same number of photons depends on the overlap between the input state of the beam splitter and a state containing only even photon numbers. Here, we propose using this even-parity detection to engineer quantum states containing only even photon-number terms. As an example, we demonstrate the ability to prepare superpositions of two coherent states with opposite amplitudes, i.e. two-component Schrödinger cat states. Our scheme can prepare cat states of arbitrary size with nearly perfect fidelity. Moreover, we investigate engineering more complex even-parity states such as four-component cat states by iteratively applying our even-parity detector.

scholarly journals Generation and manipulation of Schrödinger cat states in Rydberg atom arrays

Science ◽  
2019 ◽  
Vol 365 (6453) ◽  
pp. 570-574 ◽  
Author(s):  
A. Omran ◽  
H. Levine ◽  
A. Keesling ◽  
G. Semeghini ◽  
T. T. Wang ◽  
...  
Keyword(s):  
Neutral Atom ◽  
Quantum Information Processing ◽  
Rydberg States ◽  
Rydberg Atom ◽  
Quantum Metrology ◽  
Many Body ◽  
Schrödinger Cat ◽  
Quantum Simulator ◽  
Cat States ◽  
The Many

Quantum entanglement involving coherent superpositions of macroscopically distinct states is among the most striking features of quantum theory, but its realization is challenging because such states are extremely fragile. Using a programmable quantum simulator based on neutral atom arrays with interactions mediated by Rydberg states, we demonstrate the creation of “Schrödinger cat” states of the Greenberger-Horne-Zeilinger (GHZ) type with up to 20 qubits. Our approach is based on engineering the energy spectrum and using optimal control of the many-body system. We further demonstrate entanglement manipulation by using GHZ states to distribute entanglement to distant sites in the array, establishing important ingredients for quantum information processing and quantum metrology.

scholarly journals Schrödinger cat states in circuit QED

2019 ◽  
pp. 402-427
Author(s):  
Steven M. Girvin
Keyword(s):  
Quantum Optics ◽  
Error Correction ◽  
Cavity Qed ◽  
Photon Number ◽  
Quantum Error Correction ◽  
Circuit Qed ◽  
Schrödinger Cat ◽  
Microwave Regime ◽  
Cat States ◽  
Quantum Error

Circuit quantum electrodynamics (‘circuit QED’) describes the quantum mechanics and quantum optics of superconducting electrical circuits operating in the microwave regime near absolute zero temperature. It is the analog of cavity QED in quantum optics with the role of the atoms being played by superconducting qubits. The present lecture notes present a brief overview of circuit QED and then focus on some of the novel quantum states that can be produced and measured (via photon number parity and the Wigner function) using the strong coupling between an artificial atom and one or more cavities. Of particular importance are Schrödinger cat states of photons. Despite long being considered exemplars of frail quantum superpositions that quickly decohere, such states have recently been used as the basis for quantum error correction codes which have reached the long-sought goal of enhancing the lifetime of quantum information through active quantum error correction.

scholarly journals Large array of Schrödinger cat states facilitated by an optical waveguide

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Wui Seng Leong ◽  
Mingjie Xin ◽  
Zilong Chen ◽  
Shijie Chai ◽  
Yu Wang ◽  
...  
Keyword(s):  
Quantum Information ◽  
Quantum Physics ◽  
Quantum Information Processing ◽  
Large Array ◽  
Hollow Core ◽  
Photonic Crystal Fibre ◽  
Wide Range ◽  
Schrödinger Cat ◽  
Cat States ◽  
Photon Interactions

Abstract Quantum engineering using photonic structures offer new capabilities for atom-photon interactions for quantum optics and atomic physics, which could eventually lead to integrated quantum devices. Despite the rapid progress in the variety of structures, coherent excitation of the motional states of atoms in a photonic waveguide using guided modes has yet to be demonstrated. Here, we use the waveguide mode of a hollow-core photonic crystal fibre to manipulate the mechanical Fock states of single atoms in a harmonic potential inside the fibre. We create a large array of Schrödinger cat states, a quintessential feature of quantum physics and a key element in quantum information processing and metrology, of approximately 15000 atoms along the fibre by entangling the electronic state with the coherent harmonic oscillator state of each individual atom. Our results provide a useful step for quantum information and simulation with a wide range of photonic waveguide systems.

scholarly journals Procedure via cross-Kerr nonlinearities for encoding single logical qubit information onto four-photon decoherence-free states

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jino Heo ◽  
Seong-Gon Choi
Keyword(s):  
Quantum Information ◽  
Quantum Information Processing ◽  
Photon Number ◽  
Optical Devices ◽  
Quantum Bus ◽  
Reliable Procedure ◽  
Optical Gates ◽  
Photon Loss ◽  
Decoherence Effect ◽  
Logical Qubit

AbstractWe propose a photonic procedure using cross-Kerr nonlinearities (XKNLs) to encode single logical qubit information onto four-photon decoherence-free states. In quantum information processing, a decoherence-free subspace can secure quantum information against collective decoherence. Therefore, we design a procedure employing nonlinear optical gates, which are composed of XKNLs, quantum bus beams, and photon-number-resolving measurements with linear optical devices, to conserve quantum information by encoding quantum information onto four-photon decoherence-free states (single logical qubit information). Based on our analysis in quantifying the affection (photon loss and dephasing) of the decoherence effect, we demonstrate the experimental condition to acquire the reliable procedure of single logical qubit information having the robustness against the decoherence effect.

Generation of optical Schrödinger cat states in intense laser–matter interactions

2021 ◽  
Vol 17 (10) ◽  
pp. 1104-1108 ◽  
Author(s):  
M. Lewenstein ◽  
M. F. Ciappina ◽  
E. Pisanty ◽  
J. Rivera-Dean ◽  
P. Stammer ◽  
...  
Keyword(s):  
Intense Laser ◽  
Schrödinger Cat ◽  
Cat States

scholarly journals Phase-space studies of backscattering diffraction of defective Schrödinger cat states

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Damian Kołaczek ◽  
Bartłomiej J. Spisak ◽  
Maciej Wołoszyn
Keyword(s):  
Phase Space ◽  
Dispersive Medium ◽  
Wigner Distribution ◽  
Interference Term ◽  
Wigner Distribution Function ◽  
The Subject ◽  
Schrödinger Cat ◽  
Cat States ◽  
Schrodinger Cat State ◽  
Space Approach

AbstractThe coherent superposition of two well separated Gaussian wavepackets, with defects caused by their imperfect preparation, is considered within the phase-space approach based on the Wigner distribution function. This generic state is called the defective Schrödinger cat state due to this imperfection which significantly modifies the interference term. Propagation of this state in the phase space is described by the Moyal equation which is solved for the case of a dispersive medium with a Gaussian barrier in the above-barrier reflection regime. Formally, this regime constitutes conditions for backscattering diffraction phenomena. Dynamical quantumness and the degree of localization in the phase space of the considered state as a function of its imperfection are the subject of the performed analysis. The obtained results allow concluding that backscattering communication based on the defective Schrödinger cat states appears to be feasible with existing experimental capabilities.

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