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Here we demonstrate a microwave-frequency, two-track acoustic beam splitter, based on a multistrip coupler design matched to four unidirectional transducers, two on each of the two acoustic tracks that make up the device. We explain the device design and its experimental implementation, showing good agreement between our model and the measured device scattering spectra. The beam splitter regime, dividing an input signal at port 1 into closely equal outputs at ports 2 and 3, is reached over a 94.7 MHz bandwidth centered at 4.79 GHz, with an output power division ratio |S₂₁/S₃₁|² = 1.1 ± 0.2. The measured bandwidth ofmore » the device is limited by the bandwidth of the transducers, rather than that of the multistrip coupler.« less

Broadband quantum-limited amplifiers play a critical role in the single-shot readout of superconducting qubits, but a popular implementation, the traveling wave parametric amplifier, involves a complex design and fabrication process. Here, we present a simple design for a Josephson parametric amplifier, using a lumped element resonator comprising a superconducting quantum interference device whose useful bandwidth is enhanced with an on-chip impedance-matching circuit. Additionally, we demonstrate a flux-coupling geometry that maximizes the coupling to the Josepson loop and minimizes spurious excitation of the amplifier resonant circuit. The amplifier, which operates in a flux-pumped mode, is demonstrated with a power gain ofmore » more than 20dB over a bandwidth of about 300MHz, where approximate noise measurements indicate quantum-limited pehrformance. A procedure is given for optimizing the bandwidth for this kind of amplifier, using a linearized circuit simulation while minimizing non-linearities.« less

Phonons, and in particular surface acoustic wave phonons, have been proposed as a means to coherently couple distant solid-state quantum systems. Individual phonons in a resonant structure can be controlled and detected by superconducting qubits, enabling the coherent generation and measurement of complex stationary phonon states. We report the deterministic emission and capture of itinerant surface acoustic wave phonons, enabling the quantum entanglement of two superconducting qubits. Using a 2-millimeter-long acoustic quantum communication channel, equivalent to a 500-nanosecond delay line, we demonstrate the emission and recapture of a phonon by one superconducting qubit, quantum state transfer between two superconducting qubitsmore » with a 67% efficiency, and, by partial transfer of a phonon, generation of an entangled Bell pair with a fidelity of 84%.« less

Quantum communication relies on the efficient generation of entanglement between remote quantum nodes, as entanglement is required to achieve and verify secure communications. Remote entanglement has been realized using a number of different probabilistic schemes, but deterministic remote entanglement has only been demonstrated recently, using a variety of superconducting circuit approaches. However, the deterministic violation of a Bell inequality, a strong measure of quantum correlation, has not been demonstrated so far in a superconducting quantum communication architecture, in part because achieving sufficiently strong correlation requires fast and accurate control of the emission and capture of the entangling photons. We presentmore » a simple and robust architecture for achieving this benchmark result in a superconducting system.« less