Fast Sideband Control of a Weakly Coupled Multimode Bosonic Memory

Journal Article · Thu Mar 13 04:00:00 EDT 2025 · TBD

OSTI ID:2553026

Huang, Jordan ^[1]; DiNapoli, J. Thomas ^[1]; Rockwood, Gavin ^[1]; Yuan, Ming ^[2]; Narasimhan, Prathyankara ^[1]; Gupta, Eesh ^[3]; Bal, Mustafa ^[4]; Crisa, Francesco ^[4]; Garattoni, Sabrina ^[4]; Lu, Yao ^[4]; Jiang, Liang ^[2]; Chakram, Srivatsan ^[1]

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1. Rutgers U., Piscataway
2. U. Chicago (main)
3. Stanford U.
4. Fermilab

Circuit quantum electrodynamics (cQED) with superconducting cavities coupled to nonlinear circuits like transmons offers a promising platform for hardware-efficient quantum information processing. We address critical challenges in realizing this architecture by weakening the dispersive coupling while also demonstrating fast, high-fidelity multimode control by dynamically amplifying gate speeds through transmon-mediated sideband interactions. This approach enables transmon-cavity SWAP gates, for which we achieve speeds up to 30 times larger than the bare dispersive coupling. Combined with transmon rotations, this allows for efficient, universal state preparation in a single cavity mode, though achieving unitary gates and extending control to multiple modes remains a challenge. In this work, we overcome this by introducing two sideband control strategies: (1) a shelving technique that prevents unwanted transitions by temporarily storing populations in sideband-transparent transmon states and (2) a method that exploits the dispersive shift to synchronize sideband transition rates across chosen photon-number pairs to implement transmon-cavity SWAP gates that are selective on photon number. We leverage these protocols to prepare Fock and binomial code states across any of ten modes of a multimode cavity with millisecond cavity coherence times. We demonstrate the encoding of a qubit from a transmon into arbitrary vacuum and Fock state superpositions, as well as entangled NOON states of cavity mode pairs— a scheme extendable to arbitrary multimode Fock encodings. Furthermore, we implement a new binomial encoding gate that converts arbitrary transmon superpositions into binomial code states in $$\qty{4}{\micro\second}$$ (less than $$1/\chi$$), achieving an average post-selected final state fidelity of $$\qty{96.3}{\percent}$$ across different fiducial input states.

• Research Organization: Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
• DOE Contract Number: 89243024CSC000002
• OSTI ID: 2553026
• Report Number(s): FERMILAB-PUB-25-0171-SQMS; arXiv:2503.10623; oai:inspirehep.net:2900014
• Journal Information: TBD, Journal Name: TBD
• Country of Publication: United States
• Language: English