16 research outputs found
Quantum interference between two single photons of different microwave frequencies
We have measured quantum interference between two single microwave photons
trapped in a superconducting resonator, whose frequencies are initially about 6
GHz apart. We accomplish this by use of a parametric frequency conversion
process that mixes the mode currents of two cavity harmonics through a
superconducting quantum interference device, and demonstrate that a two-photon
entanglement operation can be performed with high fidelity.Comment: 6 pages and 3 figure
Generating Multimode Entangled Microwaves with a Superconducting Parametric Cavity
In this Letter, we demonstrate the generation of multimode entangled states
of propagating microwaves. The entangled states are generated by parametrically
pumping a multimode superconducting cavity. By combining different pump
frequencies, applied simultaneously to the device, we can produce different
entanglement structures in a programable fashion. The Gaussian output states
are fully characterized by measuring the full covariance matrices of the modes.
The covariance matrices are absolutely calibrated using an in situ microwave
calibration source, a shot noise tunnel junction. Applying a variety of
entanglement measures, we demonstrate both full inseparability and genuine
tripartite entanglement of the states. Our method is easily extensible to more
modes.Comment: 5 pages, 1 figures, 1 tabl
Observation of two-mode squeezing in a traveling wave parametric amplifier
Traveling wave parametric amplifiers (TWPAs) have recently emerged as
essential tools for broadband near quantum-limited amplification. However,
their use to generate microwave quantum states still misses an experimental
demonstration. In this letter, we report operation of a TWPA as a source of
two-mode squeezed microwave radiation. We demonstrate broadband entanglement
generation between two modes separated by up to 400 MHz by measuring
logarithmic negativity between 0.27 and 0.51 and collective quadrature
squeezing below the vacuum limit between 1.5 and 2.1 dB. This work opens
interesting perspectives for the exploration of novel microwave photonics
experiments with possible applications in quantum sensing and continuous
variable quantum computing
Quantum superposition of a single microwave photon in two different "colour" states
The ability to coherently couple arbitrary harmonic oscillators in a
fully-controlled way is an important tool to process quantum information.
Coupling between quantum harmonic oscillators has previously been demonstrated
in several physical systems by use of a two-level system as a mediating
element. Direct interaction at the quantum level has only recently been
realized by use of resonant coupling between trapped ions. Here we implement a
tunable direct coupling between the microwave harmonics of a superconducting
resonator by use of parametric frequency conversion. We accomplish this by
coupling the mode currents of two harmonics through a superconducting quantum
interference device (SQUID) and modulating its flux at the difference (~ 7 GHz)
of the harmonic frequencies. We deterministically prepare a single-photon Fock
state and coherently manipulate it between multiple modes, effectively
controlling it in a superposition of two different "colours". This parametric
interaction can be described as a beam-splitter-like operation that couples
different frequency modes. As such, it could be used to implement linear
optical quantum computing protocols on-chip.Comment: 21 pages, 10 figure