Publications Fan YANG

2025

Preprint

• F. Yang, M. Magoni, H. Pichler Constructing Quantum Many-Body Scars from Hilbert Space Fragmentation, (2025-06-12), arXiv:2506.10806 arXiv:2506.10806 (ID: 721486) Toggle Abstract
  Quantum many-body scars (QMBS) are exotic many-body states that exhibit anomalous non-thermal behavior in an otherwise ergodic system. In this work, we demonstrate a simple, scalable and intuitive construction of QMBS in a kinetically constrained quantum model exhibiting weak Hilbert space fragmentation. We show that towers of exact QMBS can be constructed by injecting a quasiparticle excitation that partially activates the frozen regions in the lattice. Meanwhile, the inelastic collision between multiple quasiparticles allows for the construction of approximate scars, whose damping is governed by an emergent two-body loss. Our findings establish direct connections between quantum many-body scarring and Hilbert space fragmentation, paving the way for systematically constructing exact and approximate QMBS. The proposed model can be readily implemented in neutral-atom quantum simulators aided by strong Rydberg interactions.

2024

Preprint

• A. Warman, F. Yang, A. Tiwari, H. Pichler, S. Schafer-Nameki Categorical Symmetries in Spin Models with Atom Arrays, (2024-12-19), arXiv:2412.15024 arXiv:2412.15024 (ID: 721391) Toggle Abstract
  Categorical symmetries have recently been shown to generalize the classification of phases of matter, significantly broadening the traditional Landau paradigm. To test these predictions, we propose a simple spin chain model that encompasses all gapped phases and second-order phase transitions governed by the categorical symmetry Rep(D8). This model not only captures the essential features of non-invertible phases but is also straightforward enough to enable practical realization. Specifically, we outline an implementation using neutral atoms trapped in optical tweezer arrays. Employing a dual-species setup and Rydberg blockade, we propose a digital simulation approach that can efficiently implement the many-body evolution in several nontrivial quantum phases.

2011

Article

• H. Zhang, X. M. Jin, J. Yang, H. N. Dai, S. J. Yang, T. M. Zhao, J. Rui, Y. He, X. Jiang, F. Yang, G. S. Pan, Z. S. Yuan, Y. Deng, Z. B. Chen, X. H. Bao, S. Chen, B. Zhao, J. Pan Preparation and storage of frequency-uncorrelated entangled photons from cavity-enhanced spontaneous parametric downconversion, Nature Photon. 632 (2011-09-11), http://dx.doi.org/10.1038/nphoton.2011.213 doi:10.1038/nphoton.2011.213 (ID: 717980) Toggle Abstract
  The preparation and storage of photonic entanglement are central to the achievement of scalable linear optical quantum computation(LOQC). The most widely used photonic entanglement source (a spontaneous parametric downconversion (SPDC) source)is not directly suitable for storage, because its working frequency bandwidth is significantly larger than any available quantum memory. To remedy this problem, cavity-enhanced narrow-band SPDC sources have been developed. However, the storage of cavity-enhanced narrow-band entangled photons has not yet been achieved. Also, the spectral correlations between the entangled photons can make them practically useless for scalable LOQC5. Here, we report the preparation and storage of frequency-uncorrelated narrowband (5 MHz) entangled photons from a cavity-enhanced SPDC source. The frequency correlation between the entangled photons is eliminated by changing the continuous UV pumping beam to short pulses. The storage of the polarization state of a single photon, and of a photon entangled with another flying in the fibre, is demonstrated. Our work demonstrates a quantum interface between narrow-band entangled photons from cavity SPDC and atomic quantum memory, and thus provides an important tool towards the achievement of all-optical quantum information processing.