445 research outputs found
Viewpoint: Microwave quantum states beat the heat
From microwave ovens to satellite television to the GPS and data services on our mobile phones, microwave technology is everywhere today. But one technology that has so far failed to prove its worth in this wavelength regime is quantum communication that uses the states of single photons as information carriers. This is because single microwave photons, as opposed to classical microwave signals, are extremely vulnerable to noise from thermal excitations in the channels through which they travel. Two new independent studies, one by Ze-Liang Xiang at Technische Universität Wien (Vienna), Austria, and colleagues [1] and another by Benoît Vermersch at the University of Innsbruck, also in Austria, and colleagues [2] now describe a theoretical protocol for microwave quantum communication that is resilient to thermal and other types of noise. Their approach could become a powerful technique to establish fast links between superconducting data processors in a future all-microwave quantum network
Modeling Scientists as Agents. How Scientists Cope with the Challenges of the New Public Management of Science
The paper at hand applies agent-based modeling and simulations (ABMS) as a tool to reconstruct and to analyze how the science system works. A Luhmannian systems perspective is combined with a model of decision making of individual actors. Additionally, changes in the socio-political context of science, such as the introduction of „new public management\", are considered as factors affecting the functionality of the system as well as the decisions of individual scientists (e.g. where to publish their papers). Computer simulation helps to understand the complex interplay of developments at the macro (system) and the micro (actor) level.Systems Theory, Theory of Action and Decision Making, Academic Publication System, Science System, New Public Management, Agent-Based Modeling and Simulation
Superconducting cavity-electromechanics on silicon-on-insulator
Fabrication processes involving anhydrous hydrofluoric vapor etching are developed to create high-Q aluminum superconducting microwave resonators on free-standing silicon membranes formed from a silicon-on-insulator wafer. Using this fabrication process, a high-impedance 8.9-GHz coil resonator is coupled capacitively with a large participation ratio to a 9.7-MHz micromechanical resonator. Two-tone microwave spectroscopy and radiation pressure backaction are used to characterize the coupled system in a dilution refrigerator down to temperatures of T_f=11 mK, yielding a measured electromechanical vacuum coupling rate of g_0/2π = 24.6 Hz and a mechanical resonator Q factor of Q_m = 1.7 × 10^7. Microwave backaction cooling of the mechanical resonator is also studied, with a minimum phonon occupancy of n_m ≈ 16 phonons being realized at an elevated fridge temperature of T_f = 211 mK
Linear and nonlinear capacitive coupling of electro-opto-mechanical photonic crystal cavities
We fabricate and characterize a microscale silicon electro-opto-mechanical
system whose mechanical motion is coupled capacitively to an electrical circuit
and optically via radiation pressure to a photonic crystal cavity. To achieve
large electromechanical interaction strength, we implement an inverse shadow
mask fabrication scheme which obtains capacitor gaps as small as 30 nm while
maintaining a silicon surface quality necessary for minimizing optical loss.
Using the sensitive optical read-out of the photonic crystal cavity, we
characterize the linear and nonlinear capacitive coupling to the fundamental 63
MHz in-plane flexural motion of the structure, showing that the large
electromechanical coupling in such devices may be suitable for realizing
efficient microwave-to-optical signal conversion.Comment: 8 papers, 4 figure
Observation of the photon blockade breakdown phase transition
Nonequilibrium phase transitions exist in damped-driven open quantum systems when the continuous tuning of an external parameter leads to a transition between two robust steady states. In second-order transitions this change is abrupt at a critical point, whereas in first-order transitions the two phases can coexist in a critical hysteresis domain. Here, we report the observation of a first-order dissipative quantum phase transition in a driven circuit quantum electrodynamics system. It takes place when the photon blockade of the driven cavity-atom system is broken by increasing the drive power. The observed experimental signature is a bimodal phase space distribution with varying weights controlled by the drive strength. Our measurements show an improved stabilization of the classical attractors up to the millisecond range when the size of the quantum system is increased from one to three artificial atoms. The formation of such robust pointer states could be used for new quantum measurement schemes or to investigate multiphoton phases of finite-size, nonlinear, open quantum systems
Electro-optic entanglement source for microwave to telecom quantum state transfer
We propose an efficient microwave-photonic modulator as a resource for stationary entangled microwave-optical fields and develop the theory for deterministic entanglement generation and quantum state transfer in multi-resonant electro-optic systems. The device is based on a single crystal whispering gallery mode resonator integrated into a 3D-microwave cavity. The specific design relies on a new combination of thin-film technology and conventional machining that is optimized for the lowest dissipation rates in the microwave, optical, and mechanical domains. We extract important device properties from finite-element simulations and predict continuous variable entanglement generation rates on the order of a Mebit/s for optical pump powers of only a few tens of microwatts. We compare the quantum state transfer fidelities of coherent, squeezed, and non-Gaussian cat states for both teleportation and direct conversion protocols under realistic conditions. Combining the unique capabilities of circuit quantum electrodynamics with the resilience of fiber optic communication could facilitate long-distance solid-state qubit networks, new methods for quantum signal synthesis, quantum key distribution, and quantum enhanced detection, as well as more power-efficient classical sensing and modulation
Quantum electromechanics of a hypersonic crystal
Radiation pressure within engineered structures has recently been used to
couple the motion of nanomechanical objects with high sensitivity to optical
and microwave electromagnetic fields. Here, we demonstrate a form of
electromechanical crystal for coupling microwave photons and hypersonic phonons
by embedding the vacuum-gap capacitor of a superconducting resonator within a
phononic crystal acoustic cavity. Utilizing a two-photon resonance condition
for efficient microwave pumping and a phononic bandgap shield to eliminate
acoustic radiation, we demonstrate large cooperative coupling ()
between a pair of electrical resonances at GHz and an acoustic resonance at
GHz. Electrical read-out of the phonon occupancy shows that the
hypersonic acoustic mode has an intrinsic energy decay time of ms and
thermalizes close to its quantum ground-state of motion (occupancy ) at a
fridge temperature of mK. Such an electromechanical transducer is
envisioned as part of a hybrid quantum circuit architecture, capable of
interfacing to both superconducting qubits and optical photons.Comment: 16 pages, 12 figures, 8 appendice
All-optical single-shot readout of a superconducting qubit
The rapid development of superconducting quantum hardware is expected to run
into significant I/O restrictions due to the need for large-scale error
correction in a cryogenic environment. Classical data centers rely on
fiber-optic interconnects to remove similar networking bottlenecks and to allow
for reconfigurable, software-defined infrastructures. In the same spirit,
ultra-cold electro-optic links have been proposed and used to generate qubit
control signals, or to replace cryogenic readout electronics. So far, the
latter suffered from either low efficiency, low bandwidth and the need for
additional microwave drives, or breaking of Cooper pairs and qubit states. In
this work we realize electro-optic microwave photonics at millikelvin
temperatures to implement a radio-over-fiber qubit readout that does not
require any active or passive cryogenic microwave equipment. We demonstrate
all-optical single-shot-readout by means of the Jaynes-Cummings nonlinearity in
a circulator-free readout scheme. Importantly, we do not observe any direct
radiation impact on the qubit state as verified with high-fidelity
quantum-non-demolition measurements despite the absence of shielding elements.
This compatibility between superconducting circuits and telecom wavelength
light is not only a prerequisite to establish modular quantum networks, it is
also relevant for multiplexed readout of superconducting photon detectors and
classical superconducting logic. Moreover, this experiment showcases the
potential of electro-optic radiometry in harsh environments - an
electronics-free sensing principle that extends into the THz regime with
applications in radio astronomy, planetary missions and earth observation
SIGMA: Bulletin of European statistics No 2-3 1994. Statistics of services
We present the fabrication and characterization of an aluminum transmon qubit on a silicon-on-insulator substrate. Key to the qubit fabrication is the use of an anhydrous hydrofluoric vapor process which selectively removes the lossy silicon oxide buried underneath the silicon device layer. For a 5.6 GHz qubit measured dispersively by a 7.1 GHz resonator, we find T_1 = 3.5 μs and T_2* = 2.2 μs. This process in principle permits the co-fabrication of silicon photonic and mechanical elements, providing a route towards chip-scale integration of electro-opto-mechanical transducers for quantum networking of superconducting microwave quantum circuits. The additional processing steps are compatible with established fabrication techniques for aluminum transmon qubits on silicon
Quantum-enabled operation of a microwave-optical interface
Solid-state microwave systems offer strong interactions for fast quantum logic and sensing but photons at telecom wavelength are the ideal choice for high-density low-loss quantum interconnects. A general-purpose interface that can make use of single photon effects requires < 1 input noise quanta, which has remained elusive due to either low efficiency or pump induced heating. Here we demonstrate coherent electro-optic modulation on nanosecond-timescales with only 0.16+0.02−0.01 microwave input noise photons with a total bidirectional transduction efficiency of 8.7% (or up to 15% with 0.41+0.02−0.02), as required for near-term heralded quantum network protocols. The use of short and high-power optical pump pulses also enables near-unity cooperativity of the electro-optic interaction leading to an internal pure conversion efficiency of up to 99.5%. Together with the low mode occupancy this provides evidence for electro-optic laser cooling and vacuum amplification as predicted a decade ago
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