Efficient Simulation of Loop Quantum Gravity: A Scalable Linear-Optical Approach

Cohen, Lior; Brady, Anthony J.; Huang, Zichang; Liu, Hongguang; Qu, Dongxue; Dowling, Jonathan P.; Han, Muxin

doi:10.1103/physrevlett.126.020501

Cited by 13 publications

(14 citation statements)

References 38 publications

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“…We implement a non-unitary 8 × 4 quantum gate of two input qubits to three output qubits, and this gate is unitarized to a 12 × 12 transformation 42 and programmed on our processor (see Methods) 43,44 . The gate simulates the LQG quantum evolution in a 4-simplex 26 . The general LQG evolution on quantum spacetime defines the spinfoam amplitude as the analog of the Feynman amplitude, while the 4-simplex is the analog of a vertex in the Feynman diagram, so the amplitude of a 4-simplex is called the vertex amplitude in LQG.…”

Section: Chip Unitary Transformationmentioning

confidence: 99%

“…And in quantum simulation, photonic chips have been used for boson sampling 6,[20][21][22] , Gaussian boson sampling 4,7 , and quantum chemistry 23,24 . Additionally, quantum simulations have been proposed for fundamental science 25 , suitable for a photonic chip architecture 26 .…”

Section: Introductionmentioning

confidence: 99%

“…In the simulation the gate represents the spinfoam and defines the transition of the photonic state, representing the tetrahedra boundary states. When the vertex amplitudes are understood as quantum gates, the full spinfoam amplitude is constructed by the scalar products of quantum tetrahedron states after experiencing the operation of the quantum gate 26 . Now, we simulate the spinfoam transition by preparing the evolution of the simulator as the evolution of the spinfoam.…”

Section: Introductionmentioning

confidence: 99%

“…While many approaches were proposed to use quantum simulators 33,34 and computers [35][36][37] for this task, experimental demonstrations are limited in scale [38][39][40] and quantum resources 41 . Here we adapt one approach which is potentially scalable to large-scale simulations since it only requires a single photon and a single linear-optical chip per vertex 26 . This approach is particularly suitable for, but not limited to, simulating LQG.…”

Section: Introductionmentioning

confidence: 99%

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Experimental simulation of loop quantum gravity on a photonic chip

et al. 2023

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The unification of general relativity and quantum theory is one of the fascinating problems of modern physics. One leading solution is Loop Quantum Gravity (LQG). Simulating LQG may be important for providing predictions which can then be tested experimentally. However, such complex quantum simulations cannot run efficiently on classical computers, and quantum computers or simulators are needed. Here, we experimentally demonstrate quantum simulations of spinfoam amplitudes of LQG on an integrated photonics quantum processor. We simulate a basic transition of LQG and show that the derived spinfoam vertex amplitude falls within 4% error with respect to the theoretical prediction, despite experimental imperfections. We also discuss how to generalize the simulation for more complex transitions, in realistic experimental conditions, which will eventually lead to a quantum advantage demonstration as well as expand the toolbox to investigate LQG.

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Section: Chip Unitary Transformationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental simulation of loop quantum gravity on a photonic chip

et al. 2023

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“…Quantum entanglement is one of the most important resources for a variety of quantum technologies such as quantum metrology [1,2], quantum communication [3], quantum sensing [4], quantum simulation [5], and quantum imaging [6]. Producing entanglement via exploitation of the three-wave mixing process in optomechanical cavities (OMC) is an attractive and innovative process for generating entangled photons [7,8].…”

Section: Introductionmentioning

confidence: 99%

Single-mode input squeezing and tripartite entanglement in three-mode ponderomotive optomechanics simulations

Dixon¹,

Cohen²,

Bhusal³

et al. 2021

Preprint

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Quantum entanglement is a crucial resource for a wide variety of quantum technologies. However, the current state-of-art methods to generate quantum entanglement in optomechanical systems are not as efficient as all-optical methods utilizing nonlinear crystals. This article proposes a new scheme in which two single-mode squeezed light fields are injected into an optomechanical cavity. We demonstrate through our numerical simulations that the quantum entanglement can be substantially enhanced with the careful selection of squeezing strength and squeezing angle of the two quadrature squeezed light fields. Our results represent a significant improvement in output bipartite photon-photon entanglement over the previously demonstrated schemes using two coherent light fields as inputs. These simulations predict a maximum increase in Gaussian entanglement by a factor of about 6, as well as increases in the quantum noise and non-Gaussianity of the output light. This non-Gaussianity is attributed to tripartite entanglement between the two optical fields and the optomechanical oscillator (OMO). At particular squeezing angles, the Gaussianity can be increased, thus introducing a method of optically controlling the intracavity entanglement. These mechanics can benefit various optical quantum technologies utilizing optomechanical entanglement and continuous variable quantum optics.

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Loop quantum gravity’s boundary maps

Chen

Livine

2021

Class. Quantum Grav.

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In canonical quantum gravity, the presence of spatial boundaries naturally leads to boundary quantum states, representing quantum boundary conditions for the bulk fields. As a consequence, quantum states of the bulk geometry need to be upgraded to wave-functions valued in the boundary Hilbert space: the bulk becomes quantum operator acting on boundary states. We apply this to loop quantum gravity and describe spin networks with 2d boundary as wavefunctions mapping bulk holonomies to spin states on the boundary. This sets the bulk-boundary relation in a clear mathematical framework, which allows to define the boundary density matrix induced by a bulk spin network states after tracing out the bulk degrees of freedom. We ask the question of the bulk reconstruction and prove a boundary-to-bulk universal reconstruction procedure, to be understood as a purification of the mixed boundary state into a pure bulk state. We further perform a first investigation in the algebraic structure of induced boundary density matrices and show how correlations between bulk excitations, i.e. quanta of 3d geometry, get reflected into the boundary density matrix.

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Efficient Simulation of Loop Quantum Gravity: A Scalable Linear-Optical Approach

Cited by 13 publications

References 38 publications

Experimental simulation of loop quantum gravity on a photonic chip

Experimental simulation of loop quantum gravity on a photonic chip

Single-mode input squeezing and tripartite entanglement in three-mode ponderomotive optomechanics simulations

Loop quantum gravity’s boundary maps

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