diff --git a/content/Articles/From virtual Z gates to virtual Z pulses.md b/content/Articles/From virtual Z gates to virtual Z pulses.md new file mode 100644 index 0000000..68cc37f --- /dev/null +++ b/content/Articles/From virtual Z gates to virtual Z pulses.md @@ -0,0 +1,78 @@ +--- +tags: Hamiltonian-level, Theory +sort-date: 2025-09-16 +description: We develop a theory of virtual Z rotations at the Hamiltonian level. This allows Z terms to be added to the Hamiltonian at no additional cost. +--- + +[[/index|Christopher K. Long]] +and Crispin H. W. Barnes + +Preprint published: 16 September 2025 18:37:59 UTC + +DOI: [10.48550/arXiv.2509.13453](https://doi.org/10.48550/arXiv.2509.13453) + +[[PDFs/2509.13453v1.pdf|PDF Download]], [[TeX_Source/2509.13453v1.tar.gz|TeX Source Download]] + +# Abstract + +> Virtual $Z$ gates have become integral for implementing fast, high-fidelity single-qubit operations. However, virtual $Z$ gates require that the system's two-qubit gates are microwave-activated or normalise the single-qubit $Z$ rotations—the group generated by $X$, $\operatorname{SWAP}$, and arbitrary phase gates. Herein, we extend the theory of virtual $Z$ gates to the pulse-level, which underlies both gate design and the recent advancements of pulse-level quantum algorithms. These algorithms attempt to utilise the full potential of present-day noisy intermediate-scale quantum (NISQ) devices by removing overheads associated with the compilation and transpilation of gates. To extend the theory of virtual $Z$ gates, we derive a platform-agnostic theoretical framework for virtual $Z$ pulses by employing time dilations of the pulse sequences that control the quantum processor. Additionally, we provide worked examples of the implementation of virtual $Z$ pulses on both semiconductor spin qubit and superconducting quantum processor architectures. Moreover, we present a general overview of the hardware support for virtual $Z$ pulses. We find virtual $Z$ pulses (and thus, virtual $Z$ gates) can be used on hardware that, with previous methods, did not support the virtual $Z$ gate. Finally, we present two additional applications of virtual $Z$ pulses to pulse-level algorithms. First, broadening the class of Hamiltonians that can be natively simulated in an analogue manner. Second, increasing the expressibility of pulse-based variational quantum algorithms. + +# Citation + +Christopher K. Long and Crispin H. W. Barnes. From virtual Z gates to virtual Z pulses, 2025, arXiv:2509.13453 [quant-ph]. + +## BibTeX + +```bibtex +@misc{long2025virtualzgatesvirtual, + title={From virtual Z gates to virtual Z pulses}, + author={Christopher K. Long and Crispin H. W. Barnes}, + year={2025}, + eprint={2509.13453}, + archivePrefix={arXiv}, + primaryClass={quant-ph}, + url={https://arxiv.org/abs/2509.13453}, +} +``` + +# Software + +- [[/Software/From-virtual-Z-gates-to-virtual-Z-pulses-source-code/index|From-virtual-Z-gates-to-virtual-Z-pulses-source-code]] [@long_2025_17149989] +- [[/Software/PySTE/index|PySTE]] [@PySTE] +- [[/Software/Suzuki-Trotter-Evolver/index|Suzuki-Trotter-Evolver]] [@SuzukiTrotterEvolver] + +# Data + +- [[/Datasets/From-virtual-Z-gates-to-virtual-Z-pulses-data]] [@long_2025_17113740] + +# Analytics + +- [Google Scholar](https://scholar.google.com/citations?view_op=view_citation&citation_for_view=GRSIcsEAAAAJ:_FxGoFyzp5QC) +- [SciRate](https://scirate.com/arxiv/2509.13453) +- [INSPIRE-HEP](https://inspirehep.net/literature/2970599) +- [Semantic Scholar](https://www.semanticscholar.org/paper/From-virtual-Z-gates-to-virtual-Z-pulses-Long-Barnes/cf6b7a932980a8ea37dfb9f0acf5b266c6260a10) + +# Social media posts + +## Bluesky + +> [!Thread] +>

Ever wanted to use virtual Z gates with arbitrary powers of SWAP? Introducing the virtual Z pulse: arxiv.org/abs/2509.13453. In our new article, we present a method for distorting a pulse sequence to implement single-qubit Z controls virtually.

[image or embed]

— Christopher K. Long (@christopher-k-long.bsky.social) 18 September 2025 at 10:33
+>

Example pulse distortions: (Top row) The modulation of a virtual Pauli-Z term in the system Hamiltonian. (2nd row) The time dilation required to implement the virtual Pauli-Z term without actually introducing it to the Hamiltonian. (3rd and 4th rows) The distorted two- and one-qubit control pulses.

[image or embed]

— Christopher K. Long (@christopher-k-long.bsky.social) 18 September 2025 at 10:33
+ +## LinkedIn + +

Ever wanted to use virtual Z gates with arbitrary powers of SWAP? Introducing the virtual Z pulse: + +C. K. Long and Prof. Crispin H. W. Barnes, From virtual Z gates to virtual Z pulses, 2025. arXiv: 2509.13453 [quant-ph]. +https://lnkd.in/eskd7xH6. + +In our new article, we present a method for distorting a pulse sequence to implement single-qubit Z controls virtually. + +Below are some example pulse distortions: The top row shows the modulation of a virtual Pauli-Z term in the system Hamiltonian. The 2nd row plots the time dilation required to implement the virtual Pauli-Z term without actually introducing it to the Hamiltonian. The 3rd and 4th rows present the distorted two- and single-qubit control pulses, respectively.

— Christopher K. Long (LinkedIn) 18 September 2025
+ +## X + +> [!Thread] +>

Ever wanted to use virtual Z gates with arbitrary powers of SWAP? Introducing the virtual Z pulse: https://t.co/Pc6UdJBgav. In our new article, we present a method for distorting a pulse sequence to implement single-qubit Z controls virtually.

— Chris Long (@Chris_K_Long45) September 18, 2025
+>

Example pulse distortions: (Top row) The modulation of a virtual Pauli-Z term in the Hamiltonian. (2nd row) The time dilation required to implement the virtual Z term without introducing it to the Hamiltonian. (3rd and 4th rows) The distorted two- and one-qubit control pulses. pic.twitter.com/ONgWLGOGR0

— Chris Long (@Chris_K_Long45) September 18, 2025
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