While quantum mechanics imposes a fundamental limit on the precision of interferometric measureme... more While quantum mechanics imposes a fundamental limit on the precision of interferometric measurements of mechanical motion due to measurement backaction, the nonlinear nature of the coupling also leads to parametric instabilities that place practical limits on the sensitivity by limiting the power in the interferometer. Such instabilities have been extensively studied in the context of gravitational wave detectors, and their presence has recently been reported in Advanced LIGO. Here, we observe experimentally and describe theoretically a new type of optomechanical instability that arises in twotone backaction-evading (BAE) measurements, a protocol designed to overcome the standard quantum limit. We demonstrate the effect in the optical domain with a photonic crystal nanobeam cavity and in the microwave domain with a micromechanical oscillator coupled to a microwave resonator. In contrast to the well-known parametric oscillatory instability that occurs in single-tone, blue-detuned pumping, and results from a two-mode squeezing interaction between the optical and mechanical modes, the parametric instability in balanced two-tone optomechanics results from single-mode squeezing of the mechanical mode in the presence of small detuning errors in the two pump frequencies. Counterintuitively, the instability occurs even in the presence of perfectly balanced intracavity fields and can occur for both signs of detuning errors. We find excellent quantitative agreement with our theoretical predictions. Since the constraints on tuning accuracy become stricter with increasing probe power, the instability imposes a fundamental limitation on BAE measurements as well as other two-tone schemes, such as dissipative squeezing of optical and microwave fields or of mechanical motion. In addition to identifying a new limitation in two-tone BAE measurements, the results also introduce a new type of nonlinear dynamics in cavity optomechanics.
Superconducting qubits are one of the most advanced candidates to realize scalable and faulttoler... more Superconducting qubits are one of the most advanced candidates to realize scalable and faulttolerant quantum computing. Despite recent significant advancements in the qubit lifetimes, the origin of the loss mechanism for state-of-the-art qubits is still subject to investigation. Moreover, successful implementation of quantum error correction requires negligible correlated errors among qubits. Here, we realize ultra-coherent superconducting transmon qubits based on niobium capacitor electrodes, with lifetimes exceeding 0.4 ms. By employing a nearly quantum-limited readout chain based on a Josephson traveling wave parametric amplifier, we are able to simultaneously record bitflip errors occurring in a multiple-qubit device, revealing that the bit-flip errors in two highly coherent qubits are strongly correlated. By introducing a novel time-resolved analysis synchronized with the operation of the pulse tube cooler in a dilution refrigerator, we find that a pulse tube mechanical shock causes nonequilibrium dynamics of the qubits, leading to correlated bit-flip errors as well as transitions outside of the computational state space. Our observations confirm that coherence improvements are still attainable in transmon qubits based on the superconducting material that has been commonly used in the field. In addition, our findings are consistent with qubit dynamics induced by two-level systems and quasiparticles, deepening our understanding of the qubit error mechanisms. Finally, these results inform possible new error-mitigation strategies by decoupling superconducting qubits from their mechanical environments.
Narrowband microwave filters have wide ranging applications, including the reduction in phase noi... more Narrowband microwave filters have wide ranging applications, including the reduction in phase noise of microwave sources within a given frequency band. The prospect of developing an automated filter that tunes itself to an arbitrary desired frequency at maximum extinction promises many experimental advantages such as an enhanced efficiency in performing fine frequency detuning scans and saving time and effort as compared to manual tuning. We design, construct, and program such an automated system and present its hardware and software for reproducibility. It consists of a cylindrical cavity filter and two motors, which change the cavity length and the coupling strength of the microwave field into the cavity, respectively. By measuring the cavity response, an algorithm implemented in Python optimizes these two parameters to achieve the tuning of the filter cavity to the desired frequency with a precision of around 20 kHz, which is significantly better than the cavity linewidth (∼1 MHz). We also demonstrate the suppression of phase noise at the desired frequency by more than 10 dB.
We introduce a quantitative measure of spin-charge separation, ζ(t) which is based on the differe... more We introduce a quantitative measure of spin-charge separation, ζ(t) which is based on the difference between the fluctuations with respect to background of the spin and charge profiles at any time t and is suitable for studying the non-equilibrium dynamics of excitations in strongly correlated systems. This quantity is not only a direct measure of the spin-charge separation in strongly correlated systems, but its long time behaviour can further serve as a possible order parameter for the interaction induced (Mott) insulating state. Within the numerically exact diagonzalization we calculate this quantity for the two dimensional Hubbard model away from Half filling. Our quantitative measure in chain, ladder and two-dimensional geometries gives the same order of magnitude for the quantity of spin-charge separation. Furthermore from the temporal behaviour of ζ(t) a threshold time can be identified that provides clues onto the breakdown of underlying Mott insulating phase.
Here we prepare the data and process scripts to reconstruct figure 4 of the paper (Two-tone optom... more Here we prepare the data and process scripts to reconstruct figure 4 of the paper (Two-tone optomechanical instability and its fundamental implications for backaction-evading measurements). The folder contains several subfolders and files: "Raw data": In this folder, you can find the raw data recorded by measurement devices during the experiment. It follows the hierarchical structure. We have three pairs of folders corresponding to three cooperativities (3.5, 7, 14). One folder of each pair contains raw data files in text format (.dat) and the other one contains plots and a Numpy dictionary of the extracted parameter for each cooperativity (superdict.npy). If you need to redo the extraction process from the raw data you can simply run "181031_CXX_Final_NOQT_BAE_2D_post_processeing.py" (XX: 3.5 or 7 or 14) python code to rewrite superdict.npy files and replot all plots in the Raw data folder.<br> "NRBcodes": A side package for the circle fit (Loren...
Here you find all raw data files and processing Python scripts for plots presented in "A cry... more Here you find all raw data files and processing Python scripts for plots presented in "A cryogenic electro-optic interconnect for superconducting devices" Amir Youssefi, et.al. Nature Electronics 2021
Here we present our study of the stress dependence in Al thin films on deposition conditions. We ... more Here we present our study of the stress dependence in Al thin films on deposition conditions. We consider two types of Al 100-nm thick films: E-beam evaporated films and films obtained by magnetron sputtering. We investigate the Al film stress hysteresis in the environment with slowly increasing and decreasing temperature, i.e. during the gradual annealing. We consider the effect of deposition temperature on the film stress and grain size. We conclude that the annealing of Al films results in increased tensile stress component and decreasing of the compressive stress. Additionally, we observe that higher deposition temperature gives higher tensile stress and greater Al grain size in the film. In order to recover the film quality and reduce the grain size, one can increase the pressure of the buffering gas during the deposition.
While quantum mechanics imposes a fundamental limit on the precision of interferometric measureme... more While quantum mechanics imposes a fundamental limit on the precision of interferometric measurements of mechanical motion due to measurement backaction, the nonlinear nature of the coupling also leads to parametric instabilities that place practical limits on the sensitivity by limiting the power in the interferometer. Such instabilities have been extensively studied in the context of gravitational wave detectors, and their presence has recently been reported in Advanced LIGO. Here we observe experimentally and describe theoretically a new type of optomechanical instability that arises in two-tone backaction-evading (BAE) measurements, designed to overcome the standard quantum limit (SQL), and demonstrate the effect in the optical domain with a photonic crystal nanobeam, and in the microwave domain with a micromechanical oscillator coupled to a microwave resonator. In contrast to the well-known oscillatory parametric instability that occurs in single-tone, blue-detuned pumping, whic...
The file is a technical drawing of a microwave filter cavity whose resonance frequency and coupli... more The file is a technical drawing of a microwave filter cavity whose resonance frequency and coupling can be tuned with two motors. In combination with a circulator, the cavity can be used to reduce the noise of microwave sources close to the carrier down to a detuning of 0.5 MHz. The properties of the filter cavity are discussed in our recent publication.
Optical computing has emerged as a promising candidate for real-time and parallel continuous data... more Optical computing has emerged as a promising candidate for real-time and parallel continuous data processing. Motivated by recent progresses in metamaterial-based analog computing, we theoretically propose a novel approach to perform two-dimensional complex mathematical operations with a simple rotated configuration. Breaking the reflection symmetry, such appealing method could realize both even and odd Green’s functions associated with any arbitrary operator. Based on the developed theory and by using Brewster effect, we demonstrate realization of a first-order differentiator. Such efficient wave-based computation method not only circumvents the major potential drawbacks of metamaterials, but also offers the most compact possible device compared to the conventional bulky lens-based optical signal and data processors.
Optical computing has emerged as a promising candidate for real-time and parallel continuous data... more Optical computing has emerged as a promising candidate for real-time and parallel continuous data processing. Motivated by recent progresses in metamaterial-based analog computing [Science 343, 160 (2014)], we theoretically investigate realization of two-dimensional complex mathematical operations using rotated configurations, recently reported in [Opt. Lett. 39, 1278 (2014)]. Breaking the reflection symmetry, such configurations could realize both even and odd Green's functions associated with spatial operators. Based on such appealing theory
While quantum mechanics imposes a fundamental limit on the precision of interferometric measureme... more While quantum mechanics imposes a fundamental limit on the precision of interferometric measurements of mechanical motion due to measurement backaction, the nonlinear nature of the coupling also leads to parametric instabilities that place practical limits on the sensitivity by limiting the power in the interferometer. Such instabilities have been extensively studied in the context of gravitational wave detectors, and their presence has recently been reported in Advanced LIGO. Here, we observe experimentally and describe theoretically a new type of optomechanical instability that arises in twotone backaction-evading (BAE) measurements, a protocol designed to overcome the standard quantum limit. We demonstrate the effect in the optical domain with a photonic crystal nanobeam cavity and in the microwave domain with a micromechanical oscillator coupled to a microwave resonator. In contrast to the well-known parametric oscillatory instability that occurs in single-tone, blue-detuned pumping, and results from a two-mode squeezing interaction between the optical and mechanical modes, the parametric instability in balanced two-tone optomechanics results from single-mode squeezing of the mechanical mode in the presence of small detuning errors in the two pump frequencies. Counterintuitively, the instability occurs even in the presence of perfectly balanced intracavity fields and can occur for both signs of detuning errors. We find excellent quantitative agreement with our theoretical predictions. Since the constraints on tuning accuracy become stricter with increasing probe power, the instability imposes a fundamental limitation on BAE measurements as well as other two-tone schemes, such as dissipative squeezing of optical and microwave fields or of mechanical motion. In addition to identifying a new limitation in two-tone BAE measurements, the results also introduce a new type of nonlinear dynamics in cavity optomechanics.
Superconducting qubits are one of the most advanced candidates to realize scalable and faulttoler... more Superconducting qubits are one of the most advanced candidates to realize scalable and faulttolerant quantum computing. Despite recent significant advancements in the qubit lifetimes, the origin of the loss mechanism for state-of-the-art qubits is still subject to investigation. Moreover, successful implementation of quantum error correction requires negligible correlated errors among qubits. Here, we realize ultra-coherent superconducting transmon qubits based on niobium capacitor electrodes, with lifetimes exceeding 0.4 ms. By employing a nearly quantum-limited readout chain based on a Josephson traveling wave parametric amplifier, we are able to simultaneously record bitflip errors occurring in a multiple-qubit device, revealing that the bit-flip errors in two highly coherent qubits are strongly correlated. By introducing a novel time-resolved analysis synchronized with the operation of the pulse tube cooler in a dilution refrigerator, we find that a pulse tube mechanical shock causes nonequilibrium dynamics of the qubits, leading to correlated bit-flip errors as well as transitions outside of the computational state space. Our observations confirm that coherence improvements are still attainable in transmon qubits based on the superconducting material that has been commonly used in the field. In addition, our findings are consistent with qubit dynamics induced by two-level systems and quasiparticles, deepening our understanding of the qubit error mechanisms. Finally, these results inform possible new error-mitigation strategies by decoupling superconducting qubits from their mechanical environments.
Narrowband microwave filters have wide ranging applications, including the reduction in phase noi... more Narrowband microwave filters have wide ranging applications, including the reduction in phase noise of microwave sources within a given frequency band. The prospect of developing an automated filter that tunes itself to an arbitrary desired frequency at maximum extinction promises many experimental advantages such as an enhanced efficiency in performing fine frequency detuning scans and saving time and effort as compared to manual tuning. We design, construct, and program such an automated system and present its hardware and software for reproducibility. It consists of a cylindrical cavity filter and two motors, which change the cavity length and the coupling strength of the microwave field into the cavity, respectively. By measuring the cavity response, an algorithm implemented in Python optimizes these two parameters to achieve the tuning of the filter cavity to the desired frequency with a precision of around 20 kHz, which is significantly better than the cavity linewidth (∼1 MHz). We also demonstrate the suppression of phase noise at the desired frequency by more than 10 dB.
We introduce a quantitative measure of spin-charge separation, ζ(t) which is based on the differe... more We introduce a quantitative measure of spin-charge separation, ζ(t) which is based on the difference between the fluctuations with respect to background of the spin and charge profiles at any time t and is suitable for studying the non-equilibrium dynamics of excitations in strongly correlated systems. This quantity is not only a direct measure of the spin-charge separation in strongly correlated systems, but its long time behaviour can further serve as a possible order parameter for the interaction induced (Mott) insulating state. Within the numerically exact diagonzalization we calculate this quantity for the two dimensional Hubbard model away from Half filling. Our quantitative measure in chain, ladder and two-dimensional geometries gives the same order of magnitude for the quantity of spin-charge separation. Furthermore from the temporal behaviour of ζ(t) a threshold time can be identified that provides clues onto the breakdown of underlying Mott insulating phase.
Here we prepare the data and process scripts to reconstruct figure 4 of the paper (Two-tone optom... more Here we prepare the data and process scripts to reconstruct figure 4 of the paper (Two-tone optomechanical instability and its fundamental implications for backaction-evading measurements). The folder contains several subfolders and files: "Raw data": In this folder, you can find the raw data recorded by measurement devices during the experiment. It follows the hierarchical structure. We have three pairs of folders corresponding to three cooperativities (3.5, 7, 14). One folder of each pair contains raw data files in text format (.dat) and the other one contains plots and a Numpy dictionary of the extracted parameter for each cooperativity (superdict.npy). If you need to redo the extraction process from the raw data you can simply run "181031_CXX_Final_NOQT_BAE_2D_post_processeing.py" (XX: 3.5 or 7 or 14) python code to rewrite superdict.npy files and replot all plots in the Raw data folder.<br> "NRBcodes": A side package for the circle fit (Loren...
Here you find all raw data files and processing Python scripts for plots presented in "A cry... more Here you find all raw data files and processing Python scripts for plots presented in "A cryogenic electro-optic interconnect for superconducting devices" Amir Youssefi, et.al. Nature Electronics 2021
Here we present our study of the stress dependence in Al thin films on deposition conditions. We ... more Here we present our study of the stress dependence in Al thin films on deposition conditions. We consider two types of Al 100-nm thick films: E-beam evaporated films and films obtained by magnetron sputtering. We investigate the Al film stress hysteresis in the environment with slowly increasing and decreasing temperature, i.e. during the gradual annealing. We consider the effect of deposition temperature on the film stress and grain size. We conclude that the annealing of Al films results in increased tensile stress component and decreasing of the compressive stress. Additionally, we observe that higher deposition temperature gives higher tensile stress and greater Al grain size in the film. In order to recover the film quality and reduce the grain size, one can increase the pressure of the buffering gas during the deposition.
While quantum mechanics imposes a fundamental limit on the precision of interferometric measureme... more While quantum mechanics imposes a fundamental limit on the precision of interferometric measurements of mechanical motion due to measurement backaction, the nonlinear nature of the coupling also leads to parametric instabilities that place practical limits on the sensitivity by limiting the power in the interferometer. Such instabilities have been extensively studied in the context of gravitational wave detectors, and their presence has recently been reported in Advanced LIGO. Here we observe experimentally and describe theoretically a new type of optomechanical instability that arises in two-tone backaction-evading (BAE) measurements, designed to overcome the standard quantum limit (SQL), and demonstrate the effect in the optical domain with a photonic crystal nanobeam, and in the microwave domain with a micromechanical oscillator coupled to a microwave resonator. In contrast to the well-known oscillatory parametric instability that occurs in single-tone, blue-detuned pumping, whic...
The file is a technical drawing of a microwave filter cavity whose resonance frequency and coupli... more The file is a technical drawing of a microwave filter cavity whose resonance frequency and coupling can be tuned with two motors. In combination with a circulator, the cavity can be used to reduce the noise of microwave sources close to the carrier down to a detuning of 0.5 MHz. The properties of the filter cavity are discussed in our recent publication.
Optical computing has emerged as a promising candidate for real-time and parallel continuous data... more Optical computing has emerged as a promising candidate for real-time and parallel continuous data processing. Motivated by recent progresses in metamaterial-based analog computing, we theoretically propose a novel approach to perform two-dimensional complex mathematical operations with a simple rotated configuration. Breaking the reflection symmetry, such appealing method could realize both even and odd Green’s functions associated with any arbitrary operator. Based on the developed theory and by using Brewster effect, we demonstrate realization of a first-order differentiator. Such efficient wave-based computation method not only circumvents the major potential drawbacks of metamaterials, but also offers the most compact possible device compared to the conventional bulky lens-based optical signal and data processors.
Optical computing has emerged as a promising candidate for real-time and parallel continuous data... more Optical computing has emerged as a promising candidate for real-time and parallel continuous data processing. Motivated by recent progresses in metamaterial-based analog computing [Science 343, 160 (2014)], we theoretically investigate realization of two-dimensional complex mathematical operations using rotated configurations, recently reported in [Opt. Lett. 39, 1278 (2014)]. Breaking the reflection symmetry, such configurations could realize both even and odd Green's functions associated with spatial operators. Based on such appealing theory
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