Low-Frequency Correlated Charge-Noise Measurements Across Multiple Energy Transitions in a Tantalum Transmon

Tennant, Daniel; Martinez, Luis A.; Beck, Kristin M.; O'Kelley, Sean; Wilen, Christopher D.; McDermott, Robert; Dubois, Jonathan; Rosen, Yaniv

doi:10.1103/prxquantum.3.030307

Cited by 21 publications

(8 citation statements)

References 56 publications

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“…Figure 4(c) shows the qubit structure zoomed in around the JJ with the locations of the one strongest coupled TLS in each trial run. The median T q 1 is around 200 µs, which is the same order of magnitude as experimentally observed qubit relaxation times [30,31]. The T q 1 drops as low as 6 µs for certain TLS distributions.…”

Section: Resultssupporting

confidence: 76%

Simulating noise on a quantum processor: interactions between a qubit and resonant two-level system bath

Cho¹,

Jasrasaria²,

Ray³

et al. 2022

Preprint

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Material defects fundamentally limit the coherence times of superconducting qubits, and manufacturing completely defect-free devices is not yet possible. Therefore, understanding the interactions between defects and a qubit in a real quantum processor design is essential. We build a model that incorporates the standard tunneling model, the electric field distributions in the qubit, and open quantum system dynamics and draw from the current understanding of two-level system (TLS) theory. Specifically, we start with one million TLSs distributed on the surface of a qubit and pick the 200 highest coupling systems. We then perform a full Lindbladian simulation that explicitly includes the coherent coupling between the qubit and the TLS bath to model the time dependent density matrix of resonant TLS defects and the qubit. We find that the 200 most strongly coupled TLSs can accurately describe the qubit energy relaxation time. This work confirms that resonant TLSs located in areas where the electric field is strong can significantly affect the qubit relaxation time, even if they are located far from the Josephson junction. Similarly, a strongly-coupled resonant TLS located in the Josephson junction does not guarantee a reduced qubit relaxation time if a more strongly coupled TLS is far from the Josephson junction. In addition to the coupling strengths between TLSs and the qubit, the model predicts that the geometry of the device and the TLS relaxation time play a significant role in qubit dynamics. Our work can provide guidance for future quantum processor designs with improved qubit coherence times.

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Section: Resultssupporting

confidence: 76%

Simulating noise on a quantum processor: interactions between a qubit and resonant two-level system bath

Cho¹,

Jasrasaria²,

Ray³

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…P (|i ) N is fitted to P (|i ) N (t) = e −t/T (i) 2 P (|i ) N (0), where T The charge-noise-induced error on the higher levels can be a problem for executing quantum algorithms. To measure the sensitivity of the charge noise, we implement a Ramsey interferometry experiment on the |2 , |3 subspace, as it is the most sensitive subspace among all three neighbouring subspaces of the four lowest transmon levels [58,59]. Our results show that the frequency shift due to charge noise is around 20 kHz, which is significantly lower than the rabi rate of a single qudit pulse (which is 20 MHz for a 50 ns long π pulse).…”

Section: Discussionmentioning

confidence: 92%

Emulating two qubits with a four-level transmon qudit for variational quantum algorithms

Cao¹,

Bakr²,

Campanaro³

et al. 2023

Preprint

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Using quantum systems with more than two levels, or qudits, can scale the computation space of quantum processors more efficiently than using qubits, which may offer an easier physical implementation for larger Hilbert spaces. However, individual qudits may exhibit larger noise, and algorithms designed for qubits require to be recompiled to qudit algorithms for execution. In this work, we implemented a two-qubit emulator using a 4-level superconducting transmon qudit for variational quantum algorithm applications and analyzed its noise model. The major source of error for the variational algorithm was readout misclassification error and amplitude damping. To improve the accuracy of the results, we applied error-mitigation techniques to reduce the effects of the misclassification and qudit decay event. The final predicted energy value is within the range of chemical accuracy. Our work demonstrates that qudits are a practical alternative to qubits for variational algorithms.

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“…We tested randomly generated optimal control pulses on two superconducting transmon quantum processors, LLNL Quantum Device and Integration Testbed (Qu-DIT)'s standard QPU and Rigetti Aspen-11. The Qu-DIT device has a single transmon made of tantalum on a sapphire substrate that has a long energy decay time [19,20]. Rigetti Aspen-11 has 47 transmons [21], and we chose one transmon among them that has good readout distinguishability up to |2 .…”

Section: Methodsmentioning

confidence: 99%

Direct pulse-level compilation of arbitrary quantum logic gates on superconducting qutrits

Cho¹,

Beck²,

Castelli³

et al. 2023

Preprint

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Advanced simulations and calculations on quantum computers require high fidelity implementations of quantum circuits. The universal gateset approach builds complex unitaries from many gates drawn from a small set of calibrated high-fidelity primitive gates, which results in a lower combined fidelity. Compiling a complex unitary for processors with higher-dimensional logical elements, such as qutrits, exacerbates the accumulated error per unitary because a longer gate sequence is needed. Optimal control methods promise time-and resource-efficient compact gate sequences and, therefore, higher fidelity. These methods generate pulses that can, in principle, directly implement any complex unitary on a quantum device. In this work, we demonstrate that any arbitrary qutrit gate can be realized with high fidelity. We generated and tested pulses for a large set of randomly selected arbitrary unitaries on two separate qutrit-compatible processors, LLNL Quantum Device and Integration Testbed (QuDIT)'s standard QPU and Rigetti Aspen-11, achieving an average fidelity around 99 %. We show that the optimal control gates do not require recalibration for at least three days and the same calibration parameters can be used for all implemented gates. Our work shows that the calibration overheads for optimal control gates can be made small enough to enable efficient quantum circuits based on this technique.

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Low-Frequency Correlated Charge-Noise Measurements Across Multiple Energy Transitions in a Tantalum Transmon

Cited by 21 publications

References 56 publications

Simulating noise on a quantum processor: interactions between a qubit and resonant two-level system bath

Simulating noise on a quantum processor: interactions between a qubit and resonant two-level system bath

Emulating two qubits with a four-level transmon qudit for variational quantum algorithms

Direct pulse-level compilation of arbitrary quantum logic gates on superconducting qutrits

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