11 research outputs found
Schr\"odinger cat states of a 16-microgram mechanical oscillator
The superposition principle is one of the most fundamental principles of
quantum mechanics. According to the Schr\"odinger equation, a physical system
can be in any linear combination of its possible states. While the validity of
this principle is routinely validated for microscopic systems, it is still
unclear why we do not observe macroscopic objects to be in superpositions of
states that can be distinguished by some classical property. Here we
demonstrate the preparation of a mechanical resonator with an effective mass of
16.2 micrograms in Schr\"odinger cat states of motion, where the constituent
atoms are in a superposition of oscillating with two opposite phases. We show
control over the size and phase of the superposition and investigate the
decoherence dynamics of these states. Apart from shedding light at the boundary
between the quantum and the classical world, our results are of interest for
quantum technologies, as they pave the way towards continuous-variable quantum
information processing and quantum metrology with mechanical resonators
Macroscopic quantum test with bulk acoustic wave resonators
Recently, solid-state mechanical resonators have become a platform for
demonstrating non-classical behavior of systems involving a truly macroscopic
number of particles. Here, we perform the most macroscopic quantum test in a
mechanical resonator to date, which probes the validity of quantum mechanics at
the microgram mass scale. This is done by a direct measurement of the Wigner
function of a high-overtone bulk acoustic wave resonator mode, monitoring the
gradual decay of negativities over tens of microseconds. While the obtained
macroscopicity of is on par with state-of-the-art atom
interferometers, future improvements of mode geometry and coherence times could
confirm the quantum superposition principle at unprecedented scales.Comment: 5+9 pages, 2+6 figures, comments are welcom
An argon ion beam milling process for native layers enabling coherent superconducting contacts
We present an argon ion beam milling process to remove the native oxide layer
forming on aluminum thin films due to their exposure to atmosphere in between
lithographic steps. Our cleaning process is readily integrable with
conventional fabrication of Josephson junction quantum circuits. From
measurements of the internal quality factors of superconducting microwave
resonators with and without contacts, we place an upper bound on the residual
resistance of an ion beam milled contact of 50 at a frequency of 4.5 GHz. Resonators for which only of the
total foot-print was exposed to the ion beam milling, in areas of low electric
and high magnetic field, showed quality factors above in the single
photon regime, and no degradation compared to single layer samples. We believe
these results will enable the development of increasingly complex
superconducting circuits for quantum information processing.Comment: 4 pages, 4 figures, supplementary materia
Two-qubit spectroscopy of spatiotemporally correlated quantum noise in superconducting qubits
Noise that exhibits significant temporal and spatial correlations across
multiple qubits can be especially harmful to both fault-tolerant quantum
computation and quantum-enhanced metrology. However, a complete spectral
characterization of the noise environment of even a two-qubit system has not
been reported thus far. We propose and experimentally validate a protocol for
two-qubit dephasing noise spectroscopy based on continuous control modulation.
By combining ideas from spin-locking relaxometry with a statistically motivated
robust estimation approach, our protocol allows for the simultaneous
reconstruction of all the single-qubit and two-qubit cross-correlation spectra,
including access to their distinctive non-classical features. Only single-qubit
control manipulations and state-tomography measurements are employed, with no
need for entangled-state preparation or readout of two-qubit observables. While
our experimental validation uses two superconducting qubits coupled to a shared
engineered noise source, our methodology is portable to a variety of
dephasing-dominated qubit architectures. By pushing quantum noise spectroscopy
beyond the single-qubit setting, our work paves the way to characterizing
spatiotemporal correlations in both engineered and naturally occurring noise
environments.Comment: total: 22 pages, 7 figures; main: 13 pages, 6 figures, supplementary:
6 pages, 1 figure; references: 3 page
Two-Qubit Spectroscopy of Spatiotemporally Correlated Quantum Noise in Superconducting Qubits
Noise that exhibits significant temporal and spatial correlations across
multiple qubits can be especially harmful to both fault-tolerant quantum
computation and quantum-enhanced metrology. However, a complete spectral
characterization of the noise environment of even a two-qubit system has not
been reported thus far. We propose and experimentally validate a protocol for
two-qubit dephasing noise spectroscopy based on continuous control modulation.
By combining ideas from spin-locking relaxometry with a statistically motivated
robust estimation approach, our protocol allows for the simultaneous
reconstruction of all the single-qubit and two-qubit cross-correlation spectra,
including access to their distinctive non-classical features. Only single-qubit
control manipulations and state-tomography measurements are employed, with no
need for entangled-state preparation or readout of two-qubit observables. While
our experimental validation uses two superconducting qubits coupled to a shared
engineered noise source, our methodology is portable to a variety of
dephasing-dominated qubit architectures. By pushing quantum noise spectroscopy
beyond the single-qubit setting, our work paves the way to characterizing
spatiotemporal correlations in both engineered and naturally occurring noise
environments
Non-Gaussian noise spectroscopy with a superconducting qubit sensor
© 2019, The Author(s). Accurate characterization of the noise influencing a quantum system of interest has far-reaching implications across quantum science, ranging from microscopic modeling of decoherence dynamics to noise-optimized quantum control. While the assumption that noise obeys Gaussian statistics is commonly employed, noise is generically non-Gaussian in nature. In particular, the Gaussian approximation breaks down whenever a qubit is strongly coupled to discrete noise sources or has a non-linear response to the environmental degrees of freedom. Thus, in order to both scrutinize the applicability of the Gaussian assumption and capture distinctive non-Gaussian signatures, a tool for characterizing non-Gaussian noise is essential. Here, we experimentally validate a quantum control protocol which, in addition to the spectrum, reconstructs the leading higher-order spectrum of engineered non-Gaussian dephasing noise using a superconducting qubit as a sensor. This first experimental demonstration of non-Gaussian noise spectroscopy represents a major step toward demonstrating a complete spectral estimation toolbox for quantum devices
Cation-Exchange Approach to Tuning the Flexibility of a Metal–Organic Framework for Gated Adsorption
Achieving
tailorable gated adsorption by tuning the dynamic behavior of a host
porous material is of great interest because of its practical application
in gas adsorption and separation. Here we devise a unique cation-exchange
approach to tune the dynamic behavior of a flexible anionic framework,
[Zn<sub>2</sub>(bptc)(datrz)]<sup>−</sup> (denoted as MAC-6,
where H<sub>4</sub>bptc = [1,1′-biphenyl]-3,3′,5,5′-tetracarboxylic
acid and Hdatrz = 3,5-diamine-1<i>H</i>-1,2,4-triazole),
so as to realize the tailorable gated adsorption. The CO<sub>2</sub> adsorption amount at 273 K can be enhanced by exchanging the counterion
of protonated dimethylamine (HDMA<sup>+</sup>) with tetraethylammonium
(TEA<sup>+</sup>), tetrabutylammonium (TBA<sup>+</sup>), and tetramethylammonium
(TMA<sup>+</sup>), where the adsorption behavior is transferred from
nongated to gated adsorption. Interestingly, the <i>P</i><sub>go</sub> for gate-opening adsorption can be further tuned from
442 to 331 mmHg by simply adjusting the ratio of HDMA<sup>+</sup> and
TMA<sup>+</sup>. The origin of this unique tunable property, as revealed
by X-ray diffraction experiments and structure models, is rooted at
the cation-responsive characteristic of this flexible framework