Digital and Real Physics

Amanda Gefter

Eva Schmidt, Pierre Silva, Pierre Schmidt

Digital twin technology -- the creation of a continuously updated virtual replica of a physical system synchronised with real-time sensor data -- has transformed performance analysis in aerospace, manufacturing, and energy sectors. Applying digital twin principles to quantum hardware offers a compelling paradigm: a quantum processor digital twin (QPDT) continuously ingests calibration data (T1/T2 times, gate error rates, crosstalk coefficients) and maintains an up-to-date computational noise model that accurately predicts circuit-level performance without running circuits on physical hardware. This paper proposes the Quantum Processor Digital Twin (QPDT) framework, a systematic methodology for constructing, calibrating, and validating digital twins for superconducting and trapped-ion quantum processors. QPDT is evaluated on 18 real quantum processors across IBM Quantum, Google Sycamore, and IonQ Aria platforms over a 90-day continuous operation period. Key results: QPDT achieves circuit fidelity prediction accuracy of 96.2% (mean absolute error 0.038 across 2,400 test circuits); twin synchronisation latency of 4.2 minutes from calibration update to model refresh; and a Quantum Twin Fidelity Score (QTFS) of 0.912. QPDT reduces hardware access requirements for algorithm benchmarking by 68% while maintaining prediction accuracy within 4% of physical execution.

Linsheng Zhong, Ruiyan Zhao, Tian Qiu +16 more

A novel physical layer digital encryption optical transmission method based on delta-sigma modulation is proposed and implemented using field programmable gate arrays (FPGA) for real-time transceivers. This approach converts ultra-high-order ciphertext, encrypted by a first-layer pseudorandom matrix, into 2-level signals via delta-sigma modulator (DSM), enabling all-digital transceiver operation with commercial optical transmission network. By employing a dynamically perturbed parameter matrix, the quantization noise introduced by the DSM is randomized, achieving a secondary masking of the ultra-high-order ciphertext. This method shares conceptual security principles with quantum noise stream cipher (QNSC) but focuses on enhancing device compatibility for physical layer secure optical transmission systems and removes the necessity for additional clock links often required by QNSC and most digital domain secure transmission technologies. In the experiment, the proposed system demonstrated bidirectional quantization noise masking physical layer secure transmission on a coarse wavelength division multiplexing (CWDM) grid, achieving a plaintext capacity of 8 × 10 Gb/s. Subsequently, real-time long-haul transmission was achieved using commercial coherent optical terminal unit (OTU4E) modules. In a 1000 km link, a 96-grid system covering the entire C-band was employed, with 9 grids measured at equal intervals across the band. Each measured grid occupied 50 GHz frequency range and achieved a plaintext transmission rate of 24.88 Gbps. This demonstrates that a potential capacity-distance product of 2.4 Pb/s·km can be achieved.

Luca Salasnich

Sunil Prajapat, Dheeraj Kumar, Pankaj Kumar +3 more

Digital twins-enabled transportation cyber-physical systems are employed in the transportation sector to enhance environmental quality, mobility, and safety. They are digital representations of transportation networks, enable the simulation of these networks’ behavior under various conditions. They can be employed in various transportation sectors, including forecasting traffic congestion, facilitate the optimization of flow and safety, enhance the efficiency of public transportation, improve the efficiency of freight transportation by offering support in this process, facilitates the consideration of future multimodal infrastructure development requirements, furnish drivers with up-to-date information about weather alerts, road closures, and traffic situations in real time, assess numerous aspects like, impacts of various mobility operators, transport users, and environmental conditions. However, the real-time data synchronization in digital twins-enabled transportation cyber-physical systems is accomplished using an open communication channel. Regrettably, the utilization of virtual-reality synthesizing security threats in the network necessitates the implementation of stringent privacy and security procedures, including authentication, encryption, and signature approaches. This study proposes a quantum-key-distribution (QKD)-based authentication protocol for secure communication of digital twins-enabled transportation cyber-physical systems. The integrated quantum in the system ensures the compactness and verifiability of data. The protocol’s security is examined using the Scyhter tool and is verified to be secure by informal security analysis. The proposed scheme achieves its efficiency over current solutions. Moreover, the latest technology and techniques are used to examine the operational capabilities and security features.