Hyperfine spin qubits in irradiated malonic acid: heat-bath algorithmic cooling

Daniel K. Park, Guanru Feng, Robabeh Rahimi, Stéphane Labruyère, Taiki Shibata, Shigeaki Nakazawa, Kazunobu Sato, Takeji Takui, Raymond Laflamme, Jonathan Baugh

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


The ability to perform quantum error correction is a significant hurdle for scalable quantum information processing. A key requirement for multiple-round quantum error correction is the ability to dynamically extract entropy from ancilla qubits. Heat-bath algorithmic cooling is a method that uses quantum logic operations to move entropy from one subsystem to another and permits cooling of a spin qubit below the closed system (Shannon) bound. Gamma-irradiated, $$^{13}$$13C-labeled malonic acid provides up to five spin qubits: one spin-half electron and four spin-half nuclei. The nuclei are strongly hyperfine-coupled to the electron and can be controlled either by exploiting the anisotropic part of the hyperfine interaction or by using pulsed electron nuclear double resonance techniques. The electron connects the nuclei to a heat-bath with a much colder effective temperature determined by the electron’s thermal spin polarization. By accurately determining the full spin Hamiltonian and performing realistic algorithmic simulations, we show that an experimental demonstration of heat-bath algorithmic cooling beyond the Shannon bound is feasible in both three-qubit and five-qubit variants of this spin system. Similar techniques could be useful for polarizing nuclei in molecular or crystalline systems that allow for non-equilibrium optical polarization of the electron spin.

Original languageEnglish
Pages (from-to)2435-2461
Number of pages27
JournalQuantum Information Processing
Issue number7
Publication statusPublished - 2015 Jul 12

Bibliographical note

Funding Information:
This research was supported by NSERC, the Canada Foundation for Innovation, CIFAR, the province of Ontario and Industry Canada. T. Takui would like to thank the support via Grants-in-Aid for Scientific Research on Innovative Areas “Quantum Cybernetics” and Scientific Research (B) from MEXT, Japan. The support for the present work by the FIRST project on “Quantum Information Processing” from JSPS, Japan, and by the AOARD project on “Quantum Properties of Molecular Nanomagnets” (Award No. FA2386-13-1-4030) is also acknowledged. We acknowledge David Cory and Richard Oakley for access to CW ESR spectrometers, Aaron Mailman for help with CW ESR, Jalil Assoud for assistance with X-ray spectroscopy, and Robert Pasuta for help with gamma-irradiation of samples. We thank Dawei Lu, Tal Mor and Yossi Weinstein for helpful discussions.

Publisher Copyright:
© 2015, Springer Science+Business Media New York.

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Statistical and Nonlinear Physics
  • Theoretical Computer Science
  • Signal Processing
  • Modelling and Simulation
  • Electrical and Electronic Engineering


Dive into the research topics of 'Hyperfine spin qubits in irradiated malonic acid: heat-bath algorithmic cooling'. Together they form a unique fingerprint.

Cite this