Observation of Three-Photon Spontaneous Parametric Down-Conversion in a Superconducting Parametric Cavity
Journal article, 2020

Spontaneous parametric down-conversion (SPDC) has been a key enabling technology in exploring quantum phenomena and their applications for decades. For instance, traditional SPDC, which splits a high-energy pump photon into two lower-energy photons, is a common way to produce entangled photon pairs. Since the early realizations of SPDC, researchers have thought to generalize it to higher order, e.g., to produce entangled photon triplets. However, directly generating photon triplets through a single SPDC process has remained elusive. Here, using a flux-pumped superconducting parametric cavity, we demonstrate direct three-photon SPDC, with photon triplets generated in a single cavity mode or split between multiple modes. With strong pumping, the states can be quite bright, with flux densities exceeding 60 photons per second per hertz. The observed states are strongly non-Gaussian, which has important implications for potential applications. In the single-mode case, we observe a triangular star-shaped distribution of quadrature voltages, indicative of the long-predicted "star state." The observed state shows strong third-order correlations, as expected for a state generated by a cubic Hamiltonian. By pumping at the sum frequency of multiple modes, we observe strong three-body correlations between multiple modes, strikingly, in the absence of second-order correlations. We further analyze the third-order correlations under mode transformations by the symplectic symmetry group, showing that the observed transformation properties serve to "fingerprint" the specific cubic Hamiltonian that generates them. The observed non-Gaussian, third-order correlations represent an important step forward in quantum optics and may have a strong impact on quantum communication with microwave fields as well as continuous-variable quantum computation.


C. W. S. Chang

University of Waterloo

C. Sabín

CSIC - Instituto de Fisica Fundamental (IFF)

P. Forn-Díaz

Institut de Física d'Altes Energies, Bellaterra

Centro Nacional de Supercomputacion

Isaac Fernando Quijandria Diaz

Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics

A. M. Vadiraj

University of Waterloo

I. Nsanzineza

University of Waterloo

Göran Johansson

Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics

C. M. Wilson

University of Waterloo

Physical Review X

2160-3308 (ISSN)

Vol. 10 1 011011

Areas of Advance

Nanoscience and Nanotechnology (2010-2017)

Subject Categories

Astronomy, Astrophysics and Cosmology

Atom and Molecular Physics and Optics

Other Physics Topics



More information

Latest update