[1] A. Acín et al. The quantum technologies roadmap: a European Community view. New J. Phys., 20, 080201(2018).

[2] J. Wang et al. Integrated photonic quantum technologies. Nat. Photonics, 14, 273-284(2020).

[3] A. W. Elshaari et al. Hybrid integrated quantum photonic circuits. Nat. Photonics, 14, 285-298(2020).

[4] S. Rodt, S. Reitzenstein. Integrated nanophotonics for the development of fully functional quantum circuits based on on-demand single-photon emitters. APL Photonics, 6, 010901(2021).

[5] E. Pelucchi et al. The potential and global outlook of integrated photonics for quantum technologies. Nat. Rev. Phys., 4, 194-208(2022).

[6] G. Moody et al. 2022 Roadmap on integrated quantum photonics. J. Phys. Photonics, 4, 012501(2022).

[7] T. Aalto et al. Open-access 3-μm SOI waveguide platform for dense photonic integrated circuits. IEEE J. Sel. Top. Quantum Electron., 25, 1-9(2019). https://doi.org/10.1109/JSTQE.2019.2908551

[8] A. Bera et al. Ultra-low loss waveguide platform in silicon photonics. Proc. SPIE, 12006, 1200603(2022).

[9] Y. Marin et al. Ultra-high-Q racetrack on thick SOI platform through hydrogen annealing, We4E.3(2022).

[10] T. Vehmas et al. Monolithic integration of up to 40 GHz Ge photodetectors in 3  μm SOI. Proc. SPIE, 11285, 112850V(2020).

[11] M. Cherchi et al. Dramatic size reduction of waveguide bends on a micron-scale silicon photonic platform. Opt. Express, 21, 17814-17823(2013).

[12] B. Zhang et al. Compact multi-million Q resonators and 100 MHz passband filter bank in a thick-SOI photonics platform. Opt. Lett., 45, 3005-3008(2020).

[13] D. Shahwar et al. Polarization splitters for micron-scale silicon photonics. Proc. SPIE, 11691, 1169104(2021).

[14] D. Jalas et al. Faraday rotation in silicon waveguides, 141-142(2017).

[15] F. Gao et al. A modified Bosch process for smooth sidewall etching, 69-72(2011).

[16] F. Gao et al. Smooth silicon sidewall etching for waveguide structures using a modified Bosch process. J. MicroNanolithogr. MEMS MOEMS, 13, 013010(2014).

[17] R. A. Soref, J. Schmidtchen, K. Petermann. Large single-mode rib waveguides in GeSi-Si and Si-on-SiO2. IEEE J. Quantum Electron., 27, 1971-1974(1991). https://doi.org/10.1109/3.83406

[18] P.-I. Dietrich et al. In situ 3D nanoprinting of free-form coupling elements for hybrid photonic integration. Nat. Photonics, 12, 241-247(2018).

[19] T. Aalto. Broadband and polarization independent waveguide-fiber coupling, 12426-12440(2023).

[20] A. Rahim et al. Open-access silicon photonics platforms in Europe. IEEE J. Sel. Top. Quantum Electron., 25, 1-18(2019).

[21] G. Z. Mashanovich et al. Low loss silicon waveguides for the mid-infrared. Opt. Express, 19, 7112-7119(2011).

[22] P. Karioja et al. Integrated multi-wavelength mid-IR light source for gas sensing. Proc. SPIE, 10657, 106570A(2018).

[23] C. Lindner et al. High-sensitivity quantum sensing with pump-enhanced spontaneous parametric down-conversion(2022).

[24] H. Rong et al. Raman gain and nonlinear optical absorption measurements in a low-loss silicon waveguide. Appl. Phys. Lett., 85, 2196-2198(2004).

[25] A. Gil-Molina et al. Optical free-carrier generation in silicon nano-waveguides at 1550 nm. Appl. Phys. Lett., 112, 251104(2018).

[26] B. Morrison et al. Four-wave mixing and nonlinear losses in thick silicon waveguides. Opt. Lett., 41, 2418-2421(2016).

[27] M. Pagani et al. Low-error and broadband microwave frequency measurement in a silicon chip. Optica, 2, 751(2015).

[28] T. Aalto et al. Total internal reflection mirrors with ultra-low losses in 3  μm thick SOI waveguides. Proc SPIE, 9367, 93670B(2015).

[29] B. E. A. Saleh, M. C. Teich. Fundamentals of Photonics(1991).

[30] M. Cherchi, T. Aalto. Bent optical waveguide(2014).

[31] X. Jiang, H. Wu, D. Dai. Low-loss and low-crosstalk multimode waveguide bend on silicon. Opt. Express, 26, 17680-17689(2018).

[32] C. Li, D. Liu, D. Dai. Multimode silicon photonics. Nanophotonics, 8, 227-247(2019).

[33] A. Mohanty et al. Quantum interference between transverse spatial waveguide modes. Nat. Commun., 8, 14010(2017).

[34] F. Brandt et al. High-dimensional quantum gates using full-field spatial modes of photons. Optica, 7, 98-107(2020).

[35] M. Piccardo et al. Roadmap on multimode light shaping. J. Opt., 24, 013001(2021).

[36] M. Hiekkamäki et al. Observation of the quantum Gouy phase. Nat. Photonics, 16, 828-833(2022).

[37] Y. Wang, D. Dai, D. Dai. Multimode silicon photonic waveguide corner-bend. Opt. Express, 28, 9062-9071(2020).

[38] T. Aalto. Devices and methods for polarization splitting(2020).

[39] M. Harjanne, T. Aalto, M. Cherchi. Polarization rotator(2020).

[40] H. Zbinden et al. Interferometry with Faraday mirrors for quantum cryptography. Electron. Lett., 33, 586-588(1997).

[41] P. Jouguet et al. Experimental demonstration of long-distance continuous-variable quantum key distribution. Nat. Photonics, 7, 378-381(2013).

[42] M. Martinelli. A universal compensator for polarization changes induced by birefringence on a retracing beam. Opt. Commun., 72, 341-344(1989).

[43] M. Cherchi et al. MMI resonators based on metal mirrors and MMI mirrors: an experimental comparison. Opt. Express, 23, 5982-5993(2015).

[44] M. Cherchi et al. Flat-top interleavers based on single MMIs. Proc. SPIE, 11285, 112850G(2020).

[45] M. Cherchi et al. Fabrication tolerant flat-top interleavers. Proc SPIE, 10108, 101080V(2017).

[46] S. Bhat et al. Low loss devices fabricated on the open access 3 μm SOI waveguide platform at VTT(2019).

[47] A. Bera et al. Amorphous silicon waveguide escalator: monolithic integration of active components on 3-μm SOI platform. Proc. SPIE, 11285, 1128507(2020). https://doi.org/10.1117/12.2544311

[48] J. Goldstein et al. Waveguide-integrated mid-infrared photodetection using graphene on a scalable chalcogenide glass platform. Nat. Commun., 13, 3915(2022).

[49] M. A. Giambra et al. High-speed double layer graphene electro-absorption modulator on SOI waveguide. Opt. Express, 27, 20145-20155(2019).

[50] W. H. P. Pernice et al. High-speed and high-efficiency travelling wave single-photon detectors embedded in nanophotonic circuits. Nat. Commun., 3, 1325(2012).

[51] Z. H. Jiang et al. Broadband and wide field-of-view plasmonic metasurface-enabled waveplates. Sci. Rep., 4, 7511(2014).

[52] M. Khorasaninejad, F. Capasso. Metalenses: versatile multifunctional photonic components. Science, 358, eaam8100(2017).

[53] I.-C. Benea-Chelmus et al. Electro-optic spatial light modulator from an engineered organic layer. Nat. Commun., 12, 5928(2021).

[54] I.-C. Benea-Chelmus et al. Gigahertz free-space electro-optic modulators based on Mie resonances. Nat. Commun., 13, 3170(2022).

[55] S. Sabouri et al. Thermo optical phase shifter with low thermal crosstalk for SOI strip waveguide. IEEE Photonics J., 13, 1-12(2021).

[56] R. Soref, B. Bennett. Electrooptical effects in silicon. IEEE J. Quantum Electron., 23, 123-129(1987).

[57] D. W. Zheng, B. T. Smith, M. Asghari. Improved efficiency Si-photonic attenuator. Opt. Express, 16, 16754-16765(2008).

[58] E. Timurdogan et al. Electric field-induced second-order nonlinear optical effects in silicon waveguides. Nat. Photonics, 11, 200-206(2017).

[59] U. Chakraborty et al. Cryogenic operation of silicon photonic modulators based on the DC Kerr effect. Optica, 7, 1385(2020).

[60] M. Gehl et al. Operation of high-speed silicon photonic micro-disk modulators at cryogenic temperatures. Optica, 4, 374(2017).

[61] M. Burla et al. 500 GHz plasmonic Mach–Zehnder modulator enabling sub-THz microwave photonics. APL Photonics, 4, 056106(2019).

[62] M. Cherchi. Electro-optic plasmonic devices(2021).

[63] P. Habegger et al. Plasmonic 100-GHz electro-optic modulators for cryogenic applications, Tu1G.1(2022).

[64] W. Heni et al. Plasmonic IQ modulators with attojoule per bit electrical energy consumption. Nat. Commun., 10, 1-8(2019).

[65] P. Edinger et al. Silicon photonic microelectromechanical phase shifters for scalable programmable photonics. Opt. Lett., 46, 5671-5674(2021).

[66] T. Grottke et al. Optoelectromechanical phase shifter with low insertion loss and a 13π tuning range. Opt. Express, 29, 5525-5537(2021).

[67] M. Dong et al. High-speed programmable photonic circuits in a cryogenically compatible, visible-near-infrared 200 mm CMOS architecture. Nat. Photonics, 16, 59-65(2021).

[68] H. Xu et al. Design and synthesis of chromophores with enhanced electro-optic activities in both bulk and plasmonic–organic hybrid devices. Mater. Horiz., 9, 261-270(2021).

[69] A. Pizzone et al. Analysis of dark current in Ge-on-Si photodiodes at cryogenic temperatures, 1-2(2020).

[70] S. Siontas et al. Low-temperature operation of high-efficiency germanium quantum dot photodetectors in the visible and near infrared. Phys. Status Solidi A, 215, 1700453(2018).

[71] Q. Zhang et al. Low-loss and polarization-insensitive photonic integrated circuit based on micron-scale SOI platform for high density TDM PONs, 1-3(2017).

[72] N. J. D. Martinez et al. High performance waveguide-coupled Ge-on-Si linear mode avalanche photodiodes. Opt. Express, 24, 19072-19081(2016).

[73] P. Vines et al. High performance planar germanium-on-silicon single-photon avalanche diode detectors. Nat. Commun., 10, 1086(2019).

[74] Y. Salamin et al. 100 GHz plasmonic photodetector. ACS Photonics, 5, 3291-3297(2018).

[75] S. Koepfli et al. >500 GHz bandwidth graphene photodetector enabling highest-capacity plasmonic-to-plasmonic links, Th3B.5(2022).

[76] E. Mykkänen et al. Enhancement of superconductivity by amorphizing molybdenum silicide films using a focused ion beam. Nanomaterials, 10, 950(2020).

[77] M. Häußler et al. Amorphous superconducting nanowire single-photon detectors integrated with nanophotonic waveguides. APL Photonics, 5, 076106(2020).

[78] J. Chang et al. Detecting telecom single photons with 99.5–2.07+0.5% system detection efficiency and high time resolution. APL Photonics, 6, 036114(2021).

[79] F. Beutel et al. Detector-integrated on-chip QKD receiver for GHz clock rates. NPJ Quantum Inf., 7, 40(2021).

[80] B. Korzh et al. Demonstration of sub-3 ps temporal resolution with a superconducting nanowire single-photon detector. Nat. Photonics, 14, 250-255(2020).

[81] A. S. Mueller et al. Free-space coupled superconducting nanowire single-photon detector with low dark counts. Optica, 8, 1586-1587(2021).

[82] J. E. Bourassa et al. Blueprint for a scalable photonic fault-tolerant quantum computer. Quantum, 5, 392(2021).

[83] J. M. Arrazola et al. Quantum circuits with many photons on a programmable nanophotonic chip. Nature, 591, 54-60(2021).

[84] L. S. Madsen et al. Quantum computational advantage with a programmable photonic processor. Nature, 606, 75-81(2022).

[85] L. You. Superconducting nanowire single-photon detectors for quantum information. Nanophotonics, 9, 2673-2692(2020).

[86] E. Mykkänen et al. Thermionic junction devices utilizing phonon blocking. Sci. Adv., 6, eaax9191(2020).

[87] A. Kemppinen et al. Cascaded superconducting junction refrigerators: optimization and performance limits. Appl. Phys. Lett., 119, 052603(2021).

[88] J. P. Höpker et al. Integrated transition edge sensors on titanium in-diffused lithium niobate waveguides. APL Photonics, 4, 056103(2019).

[89] B. Calkins et al. High quantum-efficiency photon-number-resolving detector for photonic on-chip information processing. Opt. Express, 21, 22657(2013).

[90] M. R. J. Palosaari et al. Large 256-pixel X-ray transition-edge sensor arrays with Mo/TiW/Cu trilayers. IEEE Trans. Appl. Supercond., 25, 1-4(2015).

[91] H. Akamatsu et al. Demonstration of MHz frequency domain multiplexing readout of 37 transition edge sensors for high-resolution x-ray imaging spectrometers. Appl. Phys. Lett., 119, 182601(2021).

[92] L. Grönberg et al. Side-wall spacer passivated sub-μm Josephson junction fabrication process. Supercond. Sci. Technol., 30, 125016(2017). https://doi.org/10.1088/1361-6668/aa9411

[93] J. Luomahaara et al. Unshielded SQUID sensors for ultra-low-field magnetic resonance imaging. IEEE Trans. Appl. Supercond., 28, 1-4(2018).

[94] S. Simbierowicz et al. A flux-driven Josephson parametric amplifier for sub-GHz frequencies fabricated with side-wall passivated spacer junction technology. Supercond. Sci. Technol., 31, 105001(2018).

[95] S. Simbierowicz et al. Characterizing cryogenic amplifiers with a matched temperature-variable noise source. Rev. Sci. Instrum., 92, 034708(2021).

[96] M. Perelshtein et al. Broadband continuous variable entanglement generation using Kerr-free Josephson metamaterial(2021).

[97] Application note: photon number resolving detectors(2021).

[98] C. Cahall et al. Multi-photon detection using a conventional superconducting nanowire single-photon detector. Optica, 4, 1534-1535(2017).

[99] R. Cheng et al. A 100-pixel photon-number-resolving detector unveiling photon statistics. Nat. Photonics, 17, 112-119(2023).

[100] G. E. Hoefler et al. Foundry development of system-on-chip InP-based photonic integrated circuits. IEEE J. Sel. Top. Quantum Electron., 25, 1-17(2019).

[101] J. Lin et al. Advances in on-chip photonic devices based on lithium niobate on insulator. Photonics Res., 8, 1910-1936(2020).

[102] K. Luke et al. Wafer-scale low-loss lithium niobate photonic integrated circuits. Opt. Express, 28, 24452-24458(2020).

[103] E. Obrzud et al. Stable and compact RF-to-optical link using lithium niobate on insulator waveguides. APL Photonics, 6, 121303(2021).

[104] A. Prencipe, M. A. Baghban, K. Gallo. Tunable ultranarrowband grating filters in thin-film lithium niobate. ACS Photonics, 8, 2923-2930(2021).

[105] L. Chang et al. CSOI: beyond silicon-on-insulator photonics. Opt. Photonics News, 33, 24-32(2022).

[106] T. Komljenovic et al. Photonic integrated circuits using heterogeneous integration on silicon. Proc. IEEE, 106, 2246-2257(2018).

[107] M. Kapulainen et al. Hybrid integration of InP lasers with SOI waveguides using thermocompression bonding, 61-63(2008).

[108] N. Somaschi et al. Near-optimal single-photon sources in the solid state. Nat. Photonics, 10, 340-345(2016).

[109] E. Diamanti et al. Practical challenges in quantum key distribution. NPJ Quantum Inf., 2, npjqi201625(2016).

[110] T. K. Paraïso et al. A modulator-free quantum key distribution transmitter chip. NPJ Quantum Inf., 5, 42(2019).

[111] C. Ma et al. Silicon photonic transmitter for polarization-encoded quantum key distribution. Optica, 3, 1274-1278(2016).

[112] P. Sibson et al. Chip-based quantum key distribution. Nat. Commun., 8, 1-6(2017).

[113] P. Sibson et al. Integrated silicon photonics for high-speed quantum key distribution. Optica, 4, 172-177(2017).

[114] H. Cai et al. Silicon photonic transceiver circuit for high-speed polarization-based discrete variable quantum key distribution. Opt. Express, 25, 12282-12294(2017).

[115] D. Bunandar et al. Metropolitan quantum key distribution with silicon photonics. Phys. Rev. X, 8, 021009(2018).

[116] G. Zhang et al. An integrated silicon photonic chip platform for continuous-variable quantum key distribution. Nat. Photonics, 13, 839-842(2019).

[117] M. Avesani et al. Full daylight quantum-key-distribution at 1550 nm enabled by integrated silicon photonics. NPJ Quantum Inf., 7, 1-8(2021).

[118] T. K. Paraïso et al. A photonic integrated quantum secure communication system. Nat. Photonics, 15, 850-856(2021).

[119] L. Cao et al. Chip-based measurement-device-independent quantum key distribution using integrated silicon photonic systems. Phys. Rev. Appl., 14, 011001(2020).

[120] M. Pittaluga et al. 600-km repeater-like quantum communications with dual-band stabilization. Nat. Photonics, 15, 530-535(2021).

[121] S. Wang et al. Twin-field quantum key distribution over 830-km fibre. Nat. Photonics, 16, 154-161(2022).

[122] A. Boaron et al. Secure quantum key distribution over 421 km of optical fiber. Phys. Rev. Lett., 121, 190502(2018).

[123] M. Lucamarini et al. Overcoming the rate–distance limit of quantum key distribution without quantum repeaters. Nature, 557, 400-403(2018).

[124] D. Stucki et al. Fast and simple one-way quantum key distribution. Appl. Phys. Lett., 87, 194108(2005).

[125] A. Boaron et al. Simple 2.5 GHz time-bin quantum key distribution. Appl. Phys. Lett., 112, 171108(2018).

[126] L. C. Comandar et al. Quantum key distribution without detector vulnerabilities using optically seeded lasers. Nat. Photonics, 10, 312-315(2016).

[127] H.-L. Yin et al. Measurement-device-independent quantum key distribution over a 404 km optical fiber. Phys. Rev. Lett., 117, 190501(2016).

[128] O. Kahl et al. Spectrally multiplexed single-photon detection with hybrid superconducting nanophotonic circuits. Optica, 4, 557-562(2017).

[129] X. Zheng et al. Heterogeneously integrated, superconducting silicon-photonic platform for measurement-device-independent quantum key distribution. Adv. Photonics, 3, 055002(2021).

[130] X. Chi et al. Fractal superconducting nanowire single-photon detectors with reduced polarization sensitivity. Opt. Lett., 43, 5017-5020(2018).

[131] D. V. Reddy et al. Broadband polarization insensitivity and high detection efficiency in high-fill-factor superconducting microwire single-photon detectors. APL Photonics, 7, 051302(2022).

[132] C. Bruynsteen et al. Integrated balanced homodyne photonic–electronic detector for beyond 20 GHz shot-noise-limited measurements. Optica, 8, 1146-1152(2021).

[133] H. Forsten et al. Millimeter-wave amplifier-based noise sources in SiGe BiCMOS technology. IEEE Trans. Microwaves Theory Tech., 69, 4689-4696(2021).

[134] M. Varonen et al. Cryogenic W-band SiGe BiCMOS low-noise amplifier, 185-188(2020).

[135] S. Lischke et al. Ultra-fast germanium photodiode with 3-dB bandwidth of 265 GHz. Nat. Photonics, 15, 925-931(2021).

[136] K. C. Balram, K. Srinivasan. Piezoelectric optomechanical approaches for efficient quantum microwave‐to‐optical signal transduction: the need for co‐design. Adv. Quantum Technol., 5, 2100095(2022).

[137] J. Preskill. Quantum computing in the NISQ era and beyond. Quantum, 2, 79(2018).

[138] A preview of Bristlecone, Google’s New Quantum Processor.

[139] M. F. Gonzalez-Zalba et al. Scaling silicon-based quantum computing using CMOS technology. Nat. Electron., 4, 872-884(2021).

[140] J. Duan et al. Dispersive readout of reconfigurable ambipolar quantum dots in a silicon-on-insulator nanowire. Appl. Phys. Lett., 118, 164002(2021).

[141] S. Neyens. High volume cryogenic measurement of silicon spin qubit devices from a 300 mm process line(2022).

[142] S. G. J. Philips et al. Universal control of a six-qubit quantum processor in silicon. Nature, 609, 919-924(2022).

[143] H. Bohuslavskyi et al. Scalable on-chip multiplexing of low-noise silicon electron and hole quantum dots(2022).

[144] D. S. Holmes, A. L. Ripple, M. A. Manheimer. Energy-efficient superconducting computing—power budgets and requirements. IEEE Trans. Appl. Supercond., 23, 1701610(2013).

[145] F. Lecocq et al. Control and readout of a superconducting qubit using a photonic link. Nature, 591, 575-579(2021).

[146] B. Patra et al. Cryo-CMOS circuits and systems for quantum computing applications. IEEE J. Solid-State Circuits, 53, 309-321(2018).

[147] J. C. Bardin et al. A 28 nm bulk-CMOS 4-to-8 GHz <2 mW cryogenic pulse modulator for scalable quantum computing, 456-458(2019).

[148] X. Xue et al. Quantum logic with spin qubits crossing the surface code threshold. Nature, 601, 343-347(2022).

[149] K. K. Likharev, V. K. Semenov. RSFQ logic/memory family: a new Josephson-junction technology for sub-terahertz-clock-frequency digital systems. IEEE Trans. Appl. Supercond., 1, 3-28(1991).

[150] O. A. Mukhanov. Energy-efficient single flux quantum technology. IEEE Trans. Appl. Supercond., 21, 760-769(2011).

[151] W. Chen et al. Rapid single flux quantum T-flip flop operating up to 770 GHz. IEEE Trans. Appl. Supercond., 9, 3212-3215(1999).

[152] C. Lv et al. Improving maximum count rate of superconducting nanowire single-photon detector with small active area using series attenuator. AIP Adv., 8, 105018(2018).

[153] A. J. Annunziata et al. Reset dynamics and latching in niobium superconducting nanowire single-photon detectors. J. Appl. Phys., 108, 084507(2010).

[154] J. Münzberg et al. Superconducting nanowire single-photon detector implemented in a 2D photonic crystal cavity. Optica, 5, 658-665(2018).

[155] P. Ravindran et al. Active quenching of superconducting nanowire single photon detectors. Opt. Express, 28, 4099-4114(2020).

[156] S. Miki et al. Photon detection at 1 ns time intervals using 16-element SNSPD array with SFQ multiplexer. Opt. Lett., 46, 6015-6018(2021).

[157] Finland’s first 5-qubit quantum computer is now operational.

[158] V. Billault et al. Free space optical communication receiver based on a spatial demultiplexer and a photonic integrated coherent combining circuit. Opt. Express, 29, 33134-33143(2021).

[159] A. Gritsch et al. Narrow optical transitions in erbium-implanted silicon waveguides. Phys. Rev. X, 12, 041009(2022).