Article
Physics, Multidisciplinary
Zhixin Wang, Mingrui Xu, Xu Han, Wei Fu, Shruti Puri, S. M. Girvin, Hong X. Tang, S. Shankar, M. H. Devoret
Summary: The research introduces a new method for radiation detection based on a quantum radiometer, allowing sensitive detection of microwave radiation at the subunit photon level. Using this method, radiative cooling of a microwave resonator and precise measurement of its mode temperature can be achieved.
PHYSICAL REVIEW LETTERS
(2021)
Article
Quantum Science & Technology
Bartosz Rzepkowski, Katarzyna Roszak
Summary: A scheme for detecting qubit-environment entanglement is proposed, which only requires operations and measurements on the qubit and works for any type of interaction leading to pure dephasing, as long as the initial qubit state is pure. The detection can be done at a certain time tau after the qubit initialization in a superposition state, by comparing the post-measurement evolution to a modified evolution scheme.
QUANTUM INFORMATION PROCESSING
(2021)
Article
Chemistry, Multidisciplinary
Xin-Xin Yang, Xiao-Yan Yang, Liang-Liang Guo, Lei Du, Peng Duan, Zhi-Long Jia, Hai-Ou Li, Guo-Ping Guo
Summary: One significant source of decoherence in superconducting circuits, known as two-level systems (TLSs), is found in amorphous oxide layers. These circuits can also be utilized as spectral and temporal TLS probes. Recent advancements in superconducting qubits allow for comprehensive investigations on the physics of TLSs. In this study, the tunable Xmon qubit decoherence time and resonance frequency were measured for over 3 days to study stochastic fluctuations. Analysis of time-domain Allan deviation and frequency-domain power spectral density indicates that two TLSs near resonance with the qubit are responsible for the fluctuations. The location of these two TLSs near the junctions was determined through extracted oscillation in T1 decay.
APPLIED SCIENCES-BASEL
(2023)
Article
Multidisciplinary Sciences
R. D. Delaney, M. D. Urmey, S. Mittal, B. M. Brubaker, J. M. Kindem, P. S. Burns, C. A. Regal, K. W. Lehnert
Summary: Entangling microwave-frequency superconducting quantum processors through optical light at ambient temperature would enable secure communication and distributed quantum information processing. However, transducing quantum signals between these disparate regimes of the electro-magnetic spectrum remains an outstanding goal, and interfacing superconducting qubits with electro-optic transducers presents considerable challenges. In this study, a low-backaction electro-optomechanical transducer is used to readout a superconducting transmon qubit. The modular nature of the transducer and circuit quantum electrodynamics system enable complete isolation of the qubit from optical photons, with minimal backaction on the qubit. Improvements in the transducer bandwidth and noise levels will enable the transduction of non-classical signals from a superconducting qubit to the optical domain.
Article
Physics, Multidisciplinary
Marta Pita-Vidal, Arno Bargerbos, Rok Zitko, Lukas J. Splitthoff, Lukas Grunhaupt, Jaap J. Wesdorp, Yu Liu, Leo P. Kouwenhoven, Ramon Aguado, Bernard van Heck, Angela Kou, Christian Kraglund Andersen
Summary: Spin qubits in semiconductors are a promising platform for scalable quantum computing devices, but achieving multiqubit interactions over extended distances is challenging. Superconducting spin qubits encoded in Andreev levels provide an alternative with intrinsic spin-supercurrent coupling. This study demonstrates an electrostatically defined quantum dot Josephson junction with a spin-split doublet ground state, allowing for qubit manipulation and investigating the qubit performance using direct spin manipulation. Coupling the Andreev spin qubit with a superconducting transmon qubit shows strong coherent qubit-qubit coupling, a crucial step towards a hybrid architecture combining the advantages of both superconducting and semiconductor qubits.
Article
Physics, Multidisciplinary
Kosuke Mizuno, Takaaki Takenaka, Imran Mahboob, Shiro Saito
Summary: In this study, the effect of various loss channels on the performance of logical gates on a bosonic qubit is investigated through numerical simulations. A gate error model is developed to predict experimentally achievable gate errors for bosonic qubits, providing insights into loss mechanisms and suggesting more efficient optimization algorithms to reduce gate errors.
NEW JOURNAL OF PHYSICS
(2023)
Article
Optics
Arkaprabha Ghosal, Debarshi Das, Subhashish Banerjee
Summary: In this research, the efficacy of quantum resources for quantum teleportation were studied by considering the preparation of a pure two-qubit state and its transmission through a quantum channel. It was found that certain quantum channels have different effects on the utility of quantum teleportation depending on whether the initial state is maximally entangled or nonmaximally entangled. Additionally, nonunital channels were shown to be more effective than unital channels in producing useful states for universal quantum teleportation from nonmaximally entangled pure states.
Article
Chemistry, Multidisciplinary
Akshay A. Murthy, Paul Masih Das, Stephanie M. Ribet, Cameron Kopas, Jaeyel Lee, Matthew J. Reagor, Lin Zhou, Matthew J. Kramer, Mark C. Hersam, Mattia Checchin, Anna Grassellino, Roberto dos Reis, Vinayak P. Dravid, Alexander Romanenko
Summary: This study provides a detailed assessment of the surface oxide formed in ambient conditions for transmon test qubit devices patterned from a niobium film. The oxide exhibits varying stoichiometry and the Nb2O5 region is found to be semicrystalline with oxygen vacancies and weaker bonds between niobium and oxygen atoms.
Article
Engineering, Multidisciplinary
A. -B. A. Mohamed, Hatem Rmili, Mohamed Omri, Abdel-Haleem Abdel-Aty
Summary: This paper investigates the dynamics of two spatially separated superconducting flux qubits, initially in a maximally correlated state, without mutual interaction. The system is modeled using the master intrinsic decoherence equation with the flux-qubits-resonator interaction Hamiltonian. The effects of initial state, detuning, and decoherence on the generated oscillatory correlation dynamics and the sudden death-birth phenomenon of the two flux-qubits entanglement are examined. The results demonstrate that qubit-resonator-qubit interactions have a high ability to generate quantum interferometric power and local quantum uncertainty correlations beyond that of concurrence entanglement.
ALEXANDRIA ENGINEERING JOURNAL
(2023)
Article
Physics, Multidisciplinary
P. Naveena, R. Muthuganesan, V. K. Chandrasekar
Summary: This article studies the nonlocal correlation and the influence of decoherence on the temporal evolution of a pair of superconducting charge qubits. The results show that Josephson energy enhances the resistibility against decoherence.
PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS
(2022)
Article
Physics, Applied
Kenneth Rudinger, Guilhem J. Ribeill, Luke C. G. Govia, Matthew Ware, Erik Nielsen, Kevin Young, Thomas A. Ohki, Robin Blume-Kohout, Timothy Proctor
Summary: Midcircuit measurements are an important primitive in quantum computing, especially for quantum error correction. In this study, we used quantum instrument linear gate set tomography (QILGST) technique to characterize dispersive measurements on a superconducting Transmon qubit and investigate the impact of residual cavity photon population on measurement error.
PHYSICAL REVIEW APPLIED
(2022)
Article
Computer Science, Information Systems
Manoj Stanley, Sebastian De Graaf, Teresa Honigl-Decrinis, Tobias Lindstrom, Nick M. Ridler
Summary: This paper presents a complete 2-port calibrated S-parameter measurement setup for characterizing superconducting quantum integrated circuits and other RF integrated circuits operating at mK temperatures.
Article
Physics, Multidisciplinary
A. Opremcak, C. H. Liu, C. Wilen, K. Okubo, B. G. Christensen, D. Sank, T. C. White, A. Vainsencher, M. Giustina, A. Megrant, B. Burkett, B. L. T. Plourde, R. McDermott
Summary: The method involves mapping the state of a superconducting qubit to bright and dark cavity pointer states using a measurement resonator, achieving high-fidelity measurement without the need for quantum-limited preamplification and thresholding at room temperature. By utilizing a Josephson photomultiplier for photodetection, the protocol allows access to binary outcomes of projective quantum measurement at millikelvin temperatures. The intrinsic damping of the Josephson photomultiplier can also mitigate backaction and crosstalk associated with the measurement protocol.
Article
Physics, Applied
P. Navez, A. G. Balanov, S. E. Savel'ev, A. M. Zagoskin
Summary: By using the formalism of quantum electrodynamics, we have developed a comprehensive theoretical framework to describe the interaction between single microwave photons and an array of superconducting transmon qubits in a waveguide cavity resonator. Our analysis reveals the effects of microwave photons on the array's response to a weak probe signal, showing that high quality factor cavities provide better spectral resolution, while moderate quality factor cavities offer better sensitivity for single-photon detection. Surprisingly, our results demonstrate that even a single qubit in a cavity can detect a single-photon signal under realistic system parameters. We also discuss the influence of quantum properties and electrodynamical properties on the response of qubit arrays. This study provides an efficient theoretical foundation for the development and design of quantum devices with qubit arrays, especially those using cavities with explicit expressions for transmission or reflection.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Quantum Science & Technology
Maxime Joos, Dolev Bluvstein, Yuanqi Lyu, David Weld, Ania Bleszynski Jayich
Summary: This article introduces a method of mitigating quantum decoherence based on spectral engineering of the environmental noise, and demonstrates experimentally that it outperforms monochromatic techniques. The results are consistent with quantitative modeling, and pave the way for active decoherence protection using custom-designed waveforms applied to the environment.
NPJ QUANTUM INFORMATION
(2022)
Article
Physics, Applied
Slawomir Simbierowicz, Volodymyr Y. Monarkha, Suren Singh, Nizar Messaoudi, Philip Krantz, Russell E. Lake
Summary: This article investigates systematic errors in qubit state preparation, finding that non-idealities in qubit control lines can lead to errors. Using a data-based calibration method, the scattering parameters and insertion losses of different components are measured, and their effects on gate fidelity are analyzed through simulations.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Applied
Anita Fadavi Roudsari, Daryoush Shiri, Hampus Renberg Nilsson, Giovanna Tancredi, Amr Osman, Ida-Maria Svensson, Marina Kudra, Marcus Rommel, Jonas Bylander, Vitaly Shumeiko, Per Delsing, Per Delsing
Summary: We present the implementation of a traveling-wave parametric amplifier using three-wave mixing (3WM) that achieves near-quantum-limited performance. By utilizing superconducting nonlinear asymmetric inductive element (SNAIL) loops biased with a dc magnetic flux, we enhance the amplification by 3WM. Furthermore, we incorporate dispersion engineering features to create a stop-band at the pump's second harmonic and suppress the higher harmonics, resulting in improved amplification. With a chain of 440 SNAILs, the amplifier achieves up to 20 dB gain and a 3-dB bandwidth of 1 GHz. The added noise by the amplifier is found to be less than one photon.
APPLIED PHYSICS LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Robert Rehammar, Simone Gasparinetti
Summary: A new type of low-pass filter based on a leaky coaxial waveguide is proposed, which achieves minimal insertion loss in the passband and high attenuation in the stopband. Unlike conventional resonant filters, this filter has no parasitic leakage paths, allowing the stopband to extend to very high frequencies. Experimental results demonstrate the effectiveness of the filter, with insertion loss below 0.15 dB up to 10 GHz and over 60 dB attenuation above 70 GHz. This filter is suitable for superconducting quantum computing applications.
IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES
(2023)
News Item
Physics, Multidisciplinary
Simone Gasparinetti
Summary: The emission of light from qubits in a superconducting circuit can be controlled to determine the direction of photon propagation, allowing for information routing in quantum networks.
Article
Physics, Multidisciplinary
Shahnawaz Ahmed, Fernando Quijandria, Anton Frisk Kockum
Summary: We perform quantum process tomography (QPT) using Kraus operators to learn the process representation, ensuring that the reconstructed process is completely positive. The constrained gradient-descent (GD) approach on the Stiefel manifold is used to obtain the Kraus operators and make the process trace preserving. GD-QPT combines the advantages of compressed sensing (CS) and projected least-squares (PLS) QPT methods, allowing for reconstruction from a small number of measurements and working for larger system sizes.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Applied
Hampus Renberg Nilsson, Anita Fadavi Roudsari, Daryoush Shiri, Per Delsing, Vitaly Shumeiko
Summary: In this study, we extend the theory for a Josephson-junction traveling-wave parametric amplifier (TWPA) and propose a scheme for achieving high gain. We develop a continuous three-mode model to describe a discrete chain of Josephson junctions at high frequencies and a continuous multimode model for small frequencies with linear frequency dispersion. The gain is found to be significantly reduced in both cases due to the strong dispersion at high frequencies and up-converted modes at small frequencies. To recover the high gain, we propose engineering a chain with dispersive features and placing the pump frequency within the upper band close to the spectral cutoff.
PHYSICAL REVIEW APPLIED
(2023)
Article
Quantum Science & Technology
Christopher W. Warren, Jorge Fernandez-Pendas, Shahnawaz Ahmed, Tahereh Abad, Andreas Bengtsson, Janka Biznarova, Kamanasish Debnath, Xiu Gu, Christian Krizan, Amr Osman, Anita Fadavi Roudsari, Per Delsing, Goran Johansson, Anton Frisk Kockum, Giovanna Tancredi, Jonas Bylander
Summary: We have implemented a three-qubit gate using superconducting qubits by simultaneously applying two-qubit operations. This method can be easily extended to other quantum hardware architectures and is faster than its constituent two-qubit gates. The three-qubit gate represents a whole family of operations, increasing flexibility in quantum circuit compilation. We achieved a process fidelity of 97.90% and generated two classes of entangled states using the new gate.
NPJ QUANTUM INFORMATION
(2023)
Correction
Quantum Science & Technology
Liangyu Chen, Hang-Xi Li, Yong Lu, Christopher W. Warren, Christian J. Krizan, Sandoko Kosen, Marcus Rommel, Shahnawaz Ahmed, Amr Osman, Janka Biznarova, Anita Fadavi Roudsari, Benjamin Lienhard, Marco Caputo, Kestutis Grigoras, Leif Gronberg, Joonas Govenius, Anton Frisk Kockum, Per Delsing, Jonas Bylander, Giovanna Tancredi
NPJ QUANTUM INFORMATION
(2023)
Article
Quantum Science & Technology
Liangyu Chen, Hang-Xi Li, Yong Lu, Christopher W. Warren, Christian J. Krizan, Sandoko Kosen, Marcus Rommel, Shahnawaz Ahmed, Amr Osman, Janka Biznarova, Anita Fadavi Roudsari, Benjamin Lienhard, Marco Caputo, Kestutis Grigoras, Leif Groenberg, Joonas Govenius, Anton Frisk Kockum, Per Delsing, Jonas Bylander, Giovanna Tancredi
Summary: High-fidelity and rapid readout of qubit state is crucial for quantum computing and communication, and a prerequisite for quantum error correction. We propose a readout scheme for superconducting qubits that combines a shelving technique and two-tone excitation of the readout resonator. Using a machine-learning algorithm to post-process the measurement results further improves the fidelity of qubit-state assignment. We demonstrate single-shot frequency-multiplexed qubit readout with a 140 ns readout time and achieve high assignment fidelity without using a quantum-limited amplifier.
NPJ QUANTUM INFORMATION
(2023)
Article
Multidisciplinary Sciences
X. L. He, Yong Lu, D. Q. Bao, Hang Xue, W. B. Jiang, Z. Wang, A. F. Roudsari, Per Delsing, J. S. Tsai, Z. R. Lin
Summary: This study presents a strategy to generate and preserve cat states in coplanar superconducting circuits through fast modulation of Kerr nonlinearity, addressing the challenges of scalability and controllability. The researchers were able to prepare a 2-component cat state with high fidelity in their chip-based device.
NATURE COMMUNICATIONS
(2023)
Article
Optics
Yu Zheng, Alessandro Ferraro, Anton Frisk Kockum, Giulia Ferrini
Summary: In the field of fault-tolerant quantum computing, continuous-variable systems can protect quantum information from noise using bosonic codes. Two main categories of these codes, translation-symmetric codes and rotational-symmetric codes, have not been fully understood in terms of their relationship. This study presents an iterative protocol to convert between two instances of these codes and demonstrates the potential for universality of binomial states for all-Gaussian quantum computation.
Article
Optics
Ariadna Soro, Carlos Sanchez Munoz, Anton Frisk Kockum
Summary: The interaction between two giant atoms mediated by a structured waveguide is studied. Decoherence-free interaction is possible inside the energy band but degraded due to time delay and non-Markovian effects. Outside the band, giant atoms can interact more strongly and over longer distances compared to small atoms.
