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Single-photon induced instabilities in a cavity electromechanical device
Authors:
Tanmoy Bera,
Mridul Kandpal,
G. S. Agarwal,
Vibhor Singh
Abstract:
Cavity-electromechanical systems are extensively used for sensing and controlling the vibrations of mechanical resonators down to their quantum limit. The nonlinear radiation-pressure interaction in these systems could result in an unstable response of the mechanical resonator showing features such as frequency-combs, period-doubling bifurcations and chaos. However, due to weak light-matter intera…
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Cavity-electromechanical systems are extensively used for sensing and controlling the vibrations of mechanical resonators down to their quantum limit. The nonlinear radiation-pressure interaction in these systems could result in an unstable response of the mechanical resonator showing features such as frequency-combs, period-doubling bifurcations and chaos. However, due to weak light-matter interaction, typically these effects appear at very high driving strengths. By using polariton modes formed by a strongly coupled flux-tunable transmon and a microwave cavity, here we demonstrate an electromechanical device and achieve a single-photon coupling rate $g_0/2π$ of $160~$kHz, which is nearly 4\% of the mechanical frequency $ω_m$. Due to large $g_0/ω_m$ ratio, the device shows an unstable mechanical response resulting in frequency combs in sub-single photon limit. We systematically investigate the boundary of the unstable response and identify two important regimes governed by the optomechanical backaction and the nonlinearity of the electromagnetic mode. Such an improvement in the single-photon coupling rate and the observations of microwave frequency combs at single-photon levels may have applications in the quantum control of the motional states and critical parametric sensing. Our experiments strongly suggest the requirement of newer approaches to understand instabilities.
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Submitted 2 May, 2024; v1 submitted 13 September, 2023;
originally announced September 2023.
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Instabilities near ultrastrong coupling in microwave optomechanical cavity
Authors:
Soumya Ranjan Das,
Sourav Majumder,
Sudhir Kumar Sahu,
Ujjawal Singhal,
Tanmoy Bera,
Vibhor Singh
Abstract:
With artificially engineered systems, it is now possible to realize the coherent interaction rate, which can become comparable to the mode frequencies, a regime known as ultrastrong coupling (USC). We experimentally realize a cavity-electromechanical device using a superconducting waveguide cavity and a mechanical resonator. In the presence of a strong pump, the mechanical-polaritons splitting can…
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With artificially engineered systems, it is now possible to realize the coherent interaction rate, which can become comparable to the mode frequencies, a regime known as ultrastrong coupling (USC). We experimentally realize a cavity-electromechanical device using a superconducting waveguide cavity and a mechanical resonator. In the presence of a strong pump, the mechanical-polaritons splitting can nearly reach 81% of the mechanical frequency, overwhelming all the dissipation rates. Approaching the USC limit, the steady-state response becomes unstable. We systematically measure the boundary of the unstable response while varying the pump parameters. The unstable dynamics display rich phases, such as self-induced oscillations, period-doubling bifurcation, period-tripling oscillations, and ultimately leading to the chaotic behavior. The experimental results and their theoretical modeling suggest the importance of residual nonlinear interaction terms in the weak-dissipative regime.
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Submitted 18 August, 2023; v1 submitted 1 February, 2023;
originally announced February 2023.
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Prospects of cooling a mechanical resonator with a transmon qubit in c-QED setup
Authors:
Sourav Majumder,
Tanmoy Bera,
Vibhor Singh
Abstract:
Hybrid devices based on the superconducting qubits have emerged as a promising platform for controlling the quantum states of macroscopic resonators. The nonlinearity added by a qubit can be a valuable resource for such control. Here we study a hybrid system consisting of a mechanical resonator longitudinally coupled to a transmon qubit. The qubit readout can be done by coupling to a readout mode…
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Hybrid devices based on the superconducting qubits have emerged as a promising platform for controlling the quantum states of macroscopic resonators. The nonlinearity added by a qubit can be a valuable resource for such control. Here we study a hybrid system consisting of a mechanical resonator longitudinally coupled to a transmon qubit. The qubit readout can be done by coupling to a readout mode like in c-QED setup. The coupling between the mechanical resonator and transmon qubit can be implemented by modulation of the SQUID inductance. In such a tri-partite system, we analyze the steady-state occupation of the mechanical mode when all three modes are dispersively coupled. We use the quantum-noise and the Lindblad formalism to show that the sideband cooling of the mechanical mode to its ground state is achievable. We further experimentally demonstrate that measurements of the thermomechanical motion is possible in the dispersive limit, while maintaining a large coupling between qubit and mechanical mode. Our theoretical calculations suggest that single-photon strong coupling is within the experimental reach in such hybrid devices.
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Submitted 14 May, 2022;
originally announced May 2022.
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A fast tunable 3D-transmon architecture for superconducting qubit-based hybrid devices
Authors:
Sourav Majumder,
Tanmoy Bera,
Ramya Suresh,
Vibhor Singh
Abstract:
Superconducting qubits utilize the strong non-linearity of the Josephson junctions. Control over the Josephson nonlinearity, either by a current bias or by the magnetic flux, can be a valuable resource that brings tunability in the hybrid system consisting of superconducting qubits. To enable such a control, here we incorporate a fast-flux line for a frequency tunable transmon qubit in 3D cavity a…
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Superconducting qubits utilize the strong non-linearity of the Josephson junctions. Control over the Josephson nonlinearity, either by a current bias or by the magnetic flux, can be a valuable resource that brings tunability in the hybrid system consisting of superconducting qubits. To enable such a control, here we incorporate a fast-flux line for a frequency tunable transmon qubit in 3D cavity architecture. We investigate the flux-dependent dynamic range, relaxation from unconfined states, and the bandwidth of the flux-line. Using time-domain measurements, we probe transmon's relaxation from higher energy levels after populating the cavity with $\approx 2.1\times10^4$ photons. For the device used in the experiment, we find a resurgence time corresponding to the recovery of coherence to be 4.8~$μ$s. We use a fast-flux line to tune the qubit frequency and demonstrate the swap of a single excitation between cavity and qubit mode. By measuring the deviation in the transferred population from the theoretical prediction, we estimate the bandwidth of the flux line to be $\approx$~100~MHz, limited by the parasitic effect in the design. These results suggest that the approach taken here to implement a fast-flux line in a 3D cavity could be helpful for the hybrid devices based on the superconducting qubit.
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Submitted 1 April, 2022;
originally announced April 2022.
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Large flux-mediated coupling in hybrid electromechanical system with a transmon qubit
Authors:
Tanmoy Bera,
Sourav Majumder,
Sudhir Kumar Sahu,
Vibhor Singh
Abstract:
Control over the quantum states of a massive oscillator is important for several technological applications and to test the fundamental limits of quantum mechanics. Addition of an internal degree of freedom to the oscillator could be a valuable resource for such control. Recently, hybrid electromechanical systems using superconducting qubits, based on electric-charge mediated coupling, have been q…
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Control over the quantum states of a massive oscillator is important for several technological applications and to test the fundamental limits of quantum mechanics. Addition of an internal degree of freedom to the oscillator could be a valuable resource for such control. Recently, hybrid electromechanical systems using superconducting qubits, based on electric-charge mediated coupling, have been quite successful. Here, we realize a hybrid device, consisting of a superconducting transmon qubit and a mechanical resonator coupled using the magnetic-flux. The coupling stems from the quantum-interference of the superconducting phase across the tunnel junctions. We demonstrate a vacuum electromechanical coupling rate up to 4 kHz by making the transmon qubit resonant with the readout cavity. Consequently, thermal-motion of the mechanical resonator is detected by driving the hybridized-mode with mean-occupancy well below one photon. By tuning qubit away from the cavity, electromechanical coupling can be enhanced to 40 kHz. In this limit, a small coherent drive on the mechanical resonator results in the splitting of qubit spectrum, and we observe interference signature arising from the Landau-Zener-Stückelberg effect. With improvements in qubit coherence, this system offers a novel platform to realize rich interactions and could potentially provide full control over the quantum motional states.
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Submitted 28 October, 2020; v1 submitted 16 January, 2020;
originally announced January 2020.
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n-type SnSe$_{1-x}$ for Thermoelectric Application
Authors:
Tutul Bera,
Anup V. Sanchela,
C. V. Tomy,
Ajay D. Thakur
Abstract:
We report the synthesis of n-type SnSe$_{1-x}$ using a self-sacrificial, facile, solvo-thermal synthesis route. Electrical and thermal transport measurements suggest a low thermal conductivity and a significant thermopower in the temperature range 100 - 400\,K. We also propose the possibility of developing an all SnSe thermoelectric module.
We report the synthesis of n-type SnSe$_{1-x}$ using a self-sacrificial, facile, solvo-thermal synthesis route. Electrical and thermal transport measurements suggest a low thermal conductivity and a significant thermopower in the temperature range 100 - 400\,K. We also propose the possibility of developing an all SnSe thermoelectric module.
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Submitted 6 January, 2016; v1 submitted 5 January, 2016;
originally announced January 2016.
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Measuring the Penetration Depth Anisotropy in MgB$_2$ using Small-Angle Neutron Scattering
Authors:
D. Pal,
L. DeBeer-Schmitt,
T. Bera,
R. Cubitt,
C. D. Dewhurst,
J. Jun,
N. D. Zhigadlo,
J. Karpinski,
V. G. Kogan,
M. R. Eskildsen
Abstract:
Using small-angle neutron scattering we have measured the misalignment between an applied field of 4 kOe and the flux-line lattice in MgB$_2$, as the field is rotated away from the c axis by an angle $θ$. The measurements, performed at 4.9 K, showed the vortices canting towards the c axis for all field orientations. Using a two-band/two-gap model to calculate the magnetization we are able to fit…
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Using small-angle neutron scattering we have measured the misalignment between an applied field of 4 kOe and the flux-line lattice in MgB$_2$, as the field is rotated away from the c axis by an angle $θ$. The measurements, performed at 4.9 K, showed the vortices canting towards the c axis for all field orientations. Using a two-band/two-gap model to calculate the magnetization we are able to fit our results yielding a penetration depth anisotropy, $\glam = 1.1 \pm 0.1$.
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Submitted 13 February, 2006; v1 submitted 15 November, 2005;
originally announced November 2005.