More Like this

1. Demonstration of Quantum Channel Monitoring via Quantum Wrappers

   https://doi.org/10.1364/OFC.2023.Tu3H.4  

   On, Mehmet Berkay; Singh, Sandeep Kumar; Gul, Gamze; Kanter, Gregory S.; Proietti, Roberto; Kumar, Prem; Ben Yoo, S. J. (January 2023, Optica Publishing Group)

   We experimentally demonstrate quantum channel monitoring by wavelength-time multiplexing of classical wrapper bits with quantum payloads. Bit-error-rate measurements of 5 Gb/s classical bits infer the coincidence-to-accidental ratio of the quantum channel up to 13.3 dB. 

   more » « less
2. Thermal characterization for quantum materials

   https://doi.org/10.1063/5.0124441  

   Guo, Shucheng; Xu, Youming; Hoke, Thomas; Sohi, Gobind; Li, Shuchen; Chen, Xi (March 2023, Journal of Applied Physics)

   Recently, the study of quantum materials through thermal characterization methods has attracted much attention. These methods, although not as widely used as electrical methods, can reveal intriguing physical properties in materials that are not detectable by electrical methods, particularly in electrical insulators. A fundamental understanding of these physical properties is critical for the development of novel applications for energy conversion and storage, quantum sensing and quantum information processing. In this review, we introduce several commonly used thermal characterization methods for quantum materials, including specific heat, thermal conductivity, thermal Hall effect, and Nernst effect measurements. Important theories for the thermal properties of quantum materials are discussed. Moreover, we introduce recent research progress on thermal measurements of quantum materials. We highlight experimental studies on probing the existence of quantum spin liquids, Berry curvature, chiral anomaly, and coupling between heat carriers. We also discuss the work on investigating the quantum phase transitions and quasi-particle hydrodynamics using thermal characterization methods. These findings have significantly advanced knowledge regarding novel physical properties in quantum materials. In addition, we provide some perspectives on further investigation of novel thermal properties in quantum materials. 

   more » « less
3. Characterizing the quantum properties of ultralight dark matter: An open quantum systems approach

   https://doi.org/10.1103/PhysRevD.111.032003  

   Bernal, Jose-Daniel; Petery, Ryan B; Joven, K J; Singh, Swati (February 2025, Physical Review D)

   Obtaining insight into the constituents of dark matter and their interactions with normal matter has inspired a wide range of experimental efforts. Several approaches, particularly those involving searches for ultralight bosonic dark matter (UBDM) fields, involve the use of quantum systems or measurements performed at the limits imposed by quantum mechanics. While a classical treatment of UBDM and its detectors is satisfactory, a fully quantum description would assist in developing future detection strategies. Here, we present an open quantum systems approach that accomplishes this while providing intuition into the quantum nature of the detection process itself. Furthermore, we apply the quantum theory of optical coherence to characterize the statistical properties of the UBDM field. Using representative examples, we show that this theoretical treatment has implications in uncovering signatures of the cosmological production mechanism of the UBDM field and its galactic merger history. By adapting tools from quantum optics, this work will help facilitate the creation of novel methods to extract astrophysically relevant information from correlation measurements. Published by the American Physical Society2025 

   more » « less
4. Adaptive Phase Estimation with Squeezed Vacuum Approaching the Quantum Limit

   https://doi.org/10.22331/q-2024-09-25-1480  

   Rodríguez-García, M A; Becerra, F E (September 2024, Quantum)

   Phase estimation plays a central role in communications, sensing, and information processing. Quantum correlated states, such as squeezed states, enable phase estimation beyond the shot-noise limit, and in principle approach the ultimate quantum limit in precision, when paired with optimal quantum measurements. However, physical realizations of optimal quantum measurements for optical phase estimation with quantum-correlated states are still unknown. Here we address this problem by introducing an adaptive Gaussian measurement strategy for optical phase estimation with squeezed vacuum states that, by construction, approaches the quantum limit in precision. This strategy builds from a comprehensive set of locally optimal POVMs through rotations and homodyne measurements and uses the Adaptive Quantum State Estimation framework for optimizing the adaptive measurement process, which, under certain regularity conditions, guarantees asymptotic optimality for this quantum parameter estimation problem. As a result, the adaptive phase estimation strategy based on locally-optimal homodyne measurements achieves the quantum limit within the phase interval of $[0,\pi /2)$. Furthermore, we generalize this strategy by including heterodyne measurements, enabling phase estimation across the full range of phases from $[0,\pi )$, where squeezed vacuum allows for unambiguous phase encoding. Remarkably, for this phase interval, which is the maximum range of phases that can be encoded in squeezed vacuum, this estimation strategy maintains an asymptotic quantum-optimal performance, representing a significant advancement in quantum metrology. 

   more » « less
5. Entanglement Management through Swapping over Quantum Internets

   https://doi.org/10.1145/3626570.3626595  

   Zeng, Yiming; Zhang, Jiarui; Liu, Zhenhua; Yang, Yuanyuan (September 2023, ACM SIGMETRICS Performance Evaluation Review)

   Quantum Internet has the potential to support a wide range of applications in quantum communication and quantum computing by generating, distributing, and processing quantum information. Generating a long-distance quantum entanglement is one of the most essential functions of a quantum Internet to facilitate these applications. However, entanglement is a probabilistic process, and its success rate drops significantly as distance increases. Entanglement swapping is an efficient technique used to address this challenge. How to efficiently manage the entanglement through swapping is a fundamental yet challenging problem. In this paper, we will consider two swapping methods: (1) BSM: a classic entanglement-swapping method based on Bell State measurements that fuse two successful quantum links, (2) nfusion: a more general and efficient swapping method based on Greenberger-Horne-Zeilinger measurements, capable of fusing n successful quantum links. Our goal is to maximize the entanglement rate for multiple quantum-user pairs over the quantum Internet with an arbitrary topology. We propose efficient entanglement management algorithms that utilized the unique properties of BSM and n-fusion. Evaluation results highlight that our approach outperforms existing routing protocols. 

   more » « less