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ACM Great Lakes Symposium on VLSI (GLSVLSI)

CRISP: Control-Realization Integrity and Sequence Profiling

Navnil Choudhury, Ifana Mahbub, Kanad Basu

Published Jun 18, 2026• 0 citations
Publisher

Abstract

Superconducting quantum systems rely on microwave control paths that transform circuit-derived intent into qubit-facing waveform execution. Yet this radio-frequency (RF) control boundary is typically treated implicitly: compilation derives valid pulse-level intent, while hardware studies focus on analog behavior or downstream gate performance. As a result, cross-layer mismatches among intended control, tile operating state, and realized waveform remain underspecified, even though they can directly affect pulse fidelity, timing structure, and multi-channel coordination. In this paper, we present CRISP, a control-boundary framework for checking consistency among IntendedControl, TileState, and RealizedControl. CRISP introduces a behavioral RF-tile abstraction that models gain, phase distortion, bandwidth limitation, delay, and ringing/settling, and evaluates three pairwise consistency relations together with sequence-aware checks. Across five tile-state regimes, CRISP shows that nominal behavior can remain fully consistent while distorted states trigger distinct failure signatures, including up to 8 intended-to-realized failures, 4 intended-to-state failures, and 5 sequence violations. Under controlled sequence-stress extensions, CRISP further isolates timing drift from 9 ns to 20 ns, illegal overlap from 2 ns to 14 ns, and explicit channel mismatch. These results show that correctness at the RF control boundary is fundamentally relational rather than purely local.

DOI
10.1145/3787109.3816399

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Superconducting quantum systems rely on microwave control paths that transform circuit-derived intent into qubit-facing waveform execution. Yet this radio-frequency (RF) control boundary is typically treated implicitly: compilation derives valid pulse-level intent, while hardware studies focus on analog behavior or downstream gate performance. As a result, cross-layer mismatches among intended control, tile operating state, and realized waveform remain underspecified, even though they can directly affect pulse fidelity, timing structure, and multi-channel coordination. In this paper, we present CRISP, a control-boundary framework for checking consistency among IntendedControl, TileState, and RealizedControl. CRISP introduces a behavioral RF-tile abstraction that models gain, phase distortion, bandwidth limitation, delay, and ringing/settling, and evaluates three pairwise consistency relations together with sequence-aware checks. Across five tile-state regimes, CRISP shows that nominal behavior can remain fully consistent while distorted states trigger distinct failure signatures, including up to 8 intended-to-realized failures, 4 intended-to-state failures, and 5 sequence violations. Under controlled sequence-stress extensions, CRISP further isolates timing drift from 9 ns to 20 ns, illegal overlap from 2 ns to 14 ns, and explicit channel mismatch. These results show that correctness at the RF control boundary is fundamentally relational rather than purely local.
Accurate microwave waveform delivery is a critical requirement for superconducting-qubit control.Although pulse-shaping methods are often discussed from a quantumcontrol perspective, their practical performance also depends on electrical-engineering constraints such as baseband-equivalent control-envelope bandwidth, waveform distortion, carrier detuning, and IQ quadrature accuracy.This paper presents a compact RF-control-chain-aware simulation study of microwave pulse shaping for a nominal single-qubit Xπ operation in a three-level superconducting-qubit load model.Square, Gaussian, and derivative-removal-by-adiabatic-gate (DRAG)-style pulse envelopes are compared.As a simplified approximation of bandwidth-limited waveform delivery, a causal low-pass transfer function is applied to padded in-phase and quadrature pulse envelopes before the qubit-load simulation.The results show that shaped pulses reduce leakage relative to abrupt rectangular excitation, but finite bandwidth modifies the delivered waveform and changes the leakage response in a pulse-shape-dependent manner.For the simulated 20 ns case, low-bandwidth filtering smooths and temporally extends the delivered envelopes, while sufficiently large bandwidths approach the ideal-waveform response.The study highlights the importance of joint pulse-shape design, envelope bandwidth budgeting, detuning control, and calibration in microwave control systems for scalable quantum hardware.
Frequency-multiplexed superconducting-qubit control requires more than carrier assignment: the RF budget of a shared source can perturb multi-qubit rotations through finite bandwidth, crest factor, clipping, quantization, jitter, spurs, compression, crosstalk, and leakage. We present an RF-budgeted frame-compilation and validation workflow that combines qubit-control identity (QID) records, a MATLAB/Simulink-based circuit-informed RFSoC source-chain model, QuTiP qutrit dynamics, and Qiskit-derived algorithm workloads. QID records encode qubit-specific computational and leakage transition frequencies, pulse parameters, and drive-scale calibration, while the RF-chain profile and effective crosstalk-coupling matrix are provided as separate compiler inputs. Candidate multitone RF frames are scheduled under RF-budget constraints, propagated through the RFSoC model, decoded into computational and leakage transition frames, and evaluated in QuTiP for rotation error, leakage-aware fidelity, computational-subspace survival, and transient leakage. The studies progress from single-qutrit pulse closure to pairwise coexistence, multitone RF-frame capacity, and Bernstein-Vazirani (BV) and QAOA microwave layers extracted from Qiskit circuits. The simulations show that longer pulses improve per-frame aggregation but do not necessarily minimize time-normalized layer cost; clustered frequency maps, larger rotations, and multitone leakage stacking tighten closure. Under the nominal RF budget, a Qiskit-derived 12-qubit BV -Y90 layer closes in three validated four-tone frames at 240 ns, while QAOA mixer partitions vary with rotation angle and pulse duration. All reported results are model-based, decoherence-free simulation diagnostics rather than measured hardware fidelities or wiring-reduction claims.
Control electronics for superconducting quantum processors have strict requirements for accurate command of the sensitive quantum states of their qubits. Hinging on the purity of ultra-phase-stable oscillators to upconvert very-low-noise baseband pulses, conventional control systems can become prohibitively complex and expensive when scaling to larger quantum devices, especially as high sampling rates become desirable for fine-grained pulse shaping. Few-gigahertz radio-frequency (RF) digital-to-analog converters (DACs) present a more economical avenue for high-fidelity control while simultaneously providing greater command over the spectrum of the synthesized signal. Modern RF DACs with extra-wide bandwidths are able to directly synthesize tones above their sampling rates, thereby keeping the system clock rate at a level compatible with modern digital logic systems while still being able to generate high-frequency pulses with arbitrary profiles. We have incorporated custom superconducting qubit control logic into off-the-shelf hardware capable of low-noise pulse synthesis up to 7.5 GHz using an RF DAC clocked at 5 GHz. Our approach enables highly linear and stable microwave synthesis over a wide bandwidth, giving rise to high-resolution control and a reduced number of required signal sources per qubit. We characterize the performance of the hardware using a five-transmon superconducting device and demonstrate consistently reduced two-qubit gate error (as low as 1.8%), which we show results from superior control chain linearity compared to traditional configurations. The exceptional flexibility and stability further establish a foundation for scalable quantum control beyond intermediate-scale devices.
As the number of qubits in nascent quantum processing units increases, the connectorized RF (radio frequency) analog circuits used in first generation experiments become exceedingly complex. The physical size, cost, and electrical failure rate all become limiting factors in the extensibility of control systems. We have developed a series of compact RF mixing boards to address this challenge by integrating I/Q quadrature mixing, intermediate frequency/LO (local oscillator)/RF power level adjustments, and direct current bias fine tuning on a 40 × 80 mm2 four-layer printed circuit board with electromagnetic interference shielding. The RF mixing module is designed to work with RF and LO frequencies between 2.5 and 8.5 GHz. The typical image rejection and adjacent channel isolation are measured to be ∼27 dBc and ∼50 dB. By scanning the drive phase in a loopback test, the module short-term amplitude and phase linearity are typically measured to be 5 ×10−4 (Vpp/Vmean) and 1 ×10−3 radian (pk–pk). The operation of the RF mixing board was validated by integrating it into the room temperature control system of a superconducting quantum processor and executing randomized benchmarking characterization of single and two qubit gates. We measured a single-qubit process infidelity of 9.3(3) × 10−4 and a two-qubit process infidelity of 2.7(1) × 10−2.
High-fidelity control of superconducting qubits requires carefully shaped microwave pulses to avoid several different kinds of error at once. This article is a pedagogical bridging text aimed at upper-level undergraduate and early graduate students who have completed an introductory quantum mechanics course and a first course in quantum computing or quantum information, but who have not yet encountered the physical implementation of qubit gates. We integrate physical intuition for pulse design, analytical gate-level descriptions, and practical hardware considerations into a single, derivation-driven narrative, with explicit learning objectives. We begin with simple pulse envelopes and their spectral properties, showing how finite bandwidth produces leakage outside the computational subspace. This motivates the derivative removal by adiabatic gate (DRAG) technique, which we derive explicitly using the Magnus expansion, obtaining a clear, order-by-order account of which physical error channel appears at which order and why DRAG's cancellation is necessarily incomplete. We discuss the practical hardware realities of control pulse generation, focusing on arbitrary waveform generators (AWG), local oscillators (LO), and IQ mixing. Finally, we extend the discussion to two-qubit operation via the cross-resonance gate, and interpret how driving the control qubit at the target qubit's transition frequency necessarily produces several unwanted interaction terms alongside the desired one, and how successive generations of pulse-engineering strategies have been designed to suppress them.
As the number of qubits in nascent quantum processing units increases, the connectorized RF (radio frequency) analog circuits used in first generation experiments become exceedingly complex. The physical size, cost and electrical failure rate all become limiting factors in the extensibility of control systems. We have developed a series of compact RF mixing boards to address this challenge by integrating I/Q quadrature mixing, IF(intermediate frequency)/LO(local oscillator)/RF power level adjustments, and DC (direct current) bias fine tuning on a 40 mm $\times $ 80 mm 4-layer PCB (printed circuit board) board with EMI (electromagnetic interference) shielding. The RF mixing module is designed to work with RF and LO frequencies between 2.5 and 8.5 GHz. The typical image rejection and adjacent channel isolation are measured to be $\sim$27 dBc and $\sim50dB.Byscanningthedrivephaseinaloopbacktest,themoduleshort−termamplitudeandphaselinearityaretypicallymeasuredtobe550 dB. By scanning the drive phase in a loopback test, the module short-term amplitude and phase linearity are typically measured to be 550dB.Byscanningthedrivephaseinaloopbacktest,themoduleshort−termamplitudeandphaselinearityaretypicallymeasuredtobe5\times101010^{-4}$ (Vpp_{\mathrm{pp}}pp​/Vmean_{\mathrm{mean}}mean​) and 1$\times101010^{-3}$ radian (pk-pk). The operation of RF mixing board was validated by integrating it into the room temperature control system of a superconducting quantum processor and executing randomized benchmarking characterization of single and two qubit gates. We measured a single-qubit process infidelity of 9.3(3)×10−49.3(3) \times 10^{-4}9.3(3)×10−4 and a two-qubit process infidelity of 2.7(1)×10−22.7(1) \times 10^{-2}2.7(1)×10−2.