A Comprehensive Characterization of the Vacuum Beam Guide and Its Applications

TL;DR

This work introduces the Vacuum Beam Guide (VBG) as a low-attenuation, broad-linewidth bosonic quantum channel capable of supporting continental-scale quantum networks. By deriving a comprehensive phase-noise PSD model $S_\phi(f)$ and combining attenuation, linewidth, polarization, and dispersion analyses, the authors quantify VBG's interferometric stability and quantum capacity, projecting Terabit-per-second rates over $10^4$ km. The paper further demonstrates the applicability of VBG to DI-QKD, long-baseline quantum telescopy, and blind delegated quantum computation, including reflector designs and active noise cancellation strategies. The results suggest substantial practical impact for secure quantum communications, distributed sensing, and fault-tolerant distributed quantum computing, and outline a path toward prototype-scale implementations informed by LIGO-inspired phase-noise budgeting and targeted simulations.

Abstract

The proposed vacuum beam guide (VBG) represents an innovation in the field of quantum channel technology, guaranteeing an ultra-low level of attenuation and a broad transmission linewidth, which offers an unprecedented quantum capacity exceeding Tera-qubits per second on a continental scale. However, its stability in terms of interferometry remains unexamined. To address this gap, we have developed a comprehensive error model that captures the intrinsic phase noise power spectral density associated with VBG, thereby revealing the advantages of VBG for interferometry over existing techniques. This model facilitates a comprehensive characterization of VBG as a photonic quantum channel, thereby facilitating a detailed investigation of its potential. Our theoretical analysis demonstrates the feasibility of VBG and its expected performance in a wide range of quantum applications.

Figures (20)

• Figure 1: The illustration and performance of VBG and additional loss from different reflector models (S45M and TMRRR) under room temperature and a residue gas pressure of $P=1$Pa. The alignment relative accuracy of each lens and mirror is assumed to be $0.1\%$ for translation and $1\%$. (a) The basic design of VBG promises outstanding performance across various metrics supporting a wide range of quantum applications. (b) The attenuation factor of VBG compared to the SOTA fiber (Experimental data presented here while theoretical limit is greater than $0.01$dB assuming practical constrains) petrovich2025firstnumkam2023loss and the satellite-to-ground link (*approximate level) lu2022miciusyin2017satellite. (c)The quantum capacity of VBG under one-way protocols (Two-way protocols show similar results).
• Figure 2: Interference stability of VBG. The extra contributions from reflector is neglectable and thus are not shown here (See Appendix. \ref{['subsec:seismicAndAlignN']}). (a) Normalized phase noise power spectral density of the VBG before and after active cancellation in comparison with fiber thermal noise floor bartolo2012thermalwanser1992fundamentalduan2010intrinsic. (b) Cumulative phase noise.
• Figure 3: Summary of VBG's performance metrics and application requirements. The solid line indicates that the specific application depends on a certain performance metric, while the dotted line suggests that it may be relevant according to the concrete protocol. Here, the applications in the category of secure quantum computation include Device-Independent Quantum Key Distribution ekert1991quantumacin2007devicemasanes2011securevazirani2019fullyarnon2018practicalsekatski2021devicezhang2022devicexu2022devicezapatero2023advances (Sec. \ref{['subsec:DIQKD']}), Relativistic-QKD kravtsov2018relativisticsandfuchs2025security (Appendix. \ref{['subsec:GQC']}), Quantum Private Query giovannetti2008quantump (Appendix. \ref{['subsec:GQC']}), Quantum Position Verification buhrman2014positionbluhm2022singleallerstorfer2023making (Appendix. \ref{['subsec:QPV']}), and Multi-party Entangled State Distribution fischer2021distributingmeignant2019distributingfan2025optimizedhuang2025peerfan2025distribution (Appendix. \ref{['subsec:GQC']}); Distributed quantum sensing covers Quantum Telescope khabiboulline2019quantumkhabiboulline2019opticalgottesman2012longer (Q-Telescope, Sec. \ref{['subsec:QTelescope']}), Quantum Clocks Network giovannetti2001quantumkomar2014quantumgiovannetti2002positioning (Appendix. \ref{['subsec:clocksyncgronization']}), and Giant Optical Gyroscope brady2021framegiovinetti2024gingerinodi2024noise (Appendix. \ref{['subsec:GOG']}); And federated quantum computing consists of Quantum Data Centers liu2023dataliu2024quantum (Appendix. \ref{['subsec:LDFQC']}), Blind Quantum Computation fitzsimons2017privatemorimae2013blind (Sec. \ref{['subsec:BDQC']}), and Non-Local Quantum Computation buhrman2010nonlocalityyao1993quantumbrassard2003quantum (Appendix. \ref{['subsec:NLQC']}).
• Figure 4: DI-QKD key rate vs transmission distances using VBG channel with different fidelities at generation.
• Figure 5: Illustration and performance of Q-Telescope. (a) The light from both telescope stations are directly interfered to eliminate the position information. $D_i$ is the photon detector. (b) Precision bounded by Fisher information versus baseline, assuming different schemes for an H-band magnitude 24 stellar object under a single atmosphere coherent period.