Final Report Summary - QUANPHOCHIP (Quantum photonic chip)
PUBLISHABLE SUMMARY
Quantum physics allows many fascinating and counter-intuitive phenomenon, which are fundamentally different to our daily life experience. Quantum technology enhanced information processing holds the promises to provide exponential speed-up in computation and unconditional communication security [1]. Photon, the quanta of light, is one of the nature quantum information carriers because photon travels in the speed of light and has excellent coherence property. There have been many experimental successes in the field of quantum optics. The majority of these experiments use bulk optical elements to build optical network for performing quantum information processing tasks [2-6]. Although these demonstrations are remarkable milestones in the development of experimental photonic quantum information processing, a full-scale optical quantum information processor would require much more complicated optical network. This type of optical network requires complex optical interferometers with high-level Interferometric stability, which is a significant challenge for traditional bulk optical elements. Integrated photonics [7] provides an ideal platform for tackling this challenging task. By using well-developed lithographic techniques developed in micro- and nano-fabrication industry, one can define the on-chip photonic structures, such as waveguides, directional couplers and so on for manipulating photonic qubits. The integrated photonic platform offers excellent Interferometric phase stability and perfect mode overlapping, which are necessary for high-fidelity qubit operations.
In this project, we focus on integrated quantum Silicon photonics, which is one of the leading candidates for realizing scalable quantum information processing due to the following reasons: 1. Silicon photonics fabrication techniques are well-established in the semiconductor industry and is scalable solution with high-level device integration. The footprint of the photonic device will not only much smaller than traditional bulk optical elements, but even comparing to the recently developed photonic devices based on glass, the silicon device dimensions are at least 50 times smaller (see Fig. 1). 2. High-speed silicon optical modulators are available [8]. 3. Single-photon superconducting detectors can be integrated onto the optical waveguides made by silicon [9]. This enables high-speed and high-efficiency single-photon detection. 4. Nonlinear optical properties of silicon and other CMOS compatible material are the resources for generating photon pairs [10] and could be employed for achieving deterministic two-photon gates via coherent photon conversion [11].
Within this project, we have successfully demonstrated the following crucial components with integrated quantum silicon photonics. 1. We have demonstrated an on-chip realization of the interaction-free measurement (IFM) based on silicon photonics. An IFM harnesses the wave-particle duality of single photons to sense the presence of an object via the modification of the interference pattern, which can be accomplished even if the photon and the object haven't interacted with each other [12]. By using the quantum Zeno effect, the efficiency of an IFM can be made arbitrarily close to unity [13-14]. To implement this idea, it requires precise control in fabricating the directional couplers with designed splitting ratios for making cascade interferometers. We use coupled-mode theory to numerically simulated, designed and fabricated various directional couplers. Experimentally, we exploit the inherent advantages of the lithographically written waveguides: excellent interferometric phase stability and mode matching, and obtain multipath interference with visibility above 98%. We achieved a normalized IFM efficiency up to 68.2%, which exceeds the 50% limit of the original IFM proposal [12].
2. We develop a hybrid superconducting-photonic circuit system to show how two of its main ingredients, quantum interference and single-photon detectors, can be combined in a scalable fashion on a silicon chip [16]. We demonstrate the suitability of this approach for integrated quantum optics by interfering and detecting photon pairs directly on the chip with waveguide-coupled single-photon detectors. Using a directional coupler implemented with silicon nitride nanophotonic waveguides, we observe 97% interference visibility when measuring photon statistics with two monolithically integrated superconducting single photon detectors. The photonic circuit and detector processing are compatible with standard semiconductor thin-film technology, making it possible to implement more complex and larger scale quantum photonic circuits on silicon chips.
Figure 1. Novel opportunities for photonic quantum information processing. Free space (bulk optics), glass-, Si-chip.
References:
1. M. A. Nielsen and I. L. Chuang, Quantum computation and quantum information (Cambridge University press, Cambridge, 2000).
2. J. L. O’Brien, Science 318, 1567 (2007).
3. P. Kok, et al., Rev. Mod. Phys. 79, 135 (2007).
4. J.-W. Pan, Z.-B. Chen, M. Zukowski, H. Weinfurter, and A. Zeilinger, Rev. Mod. Phys. 84, 777 (2012).
5. J. L. O’Brien, A. Furusawa, J. Vuckovic, Nat. Photon 3, 687 (2009).
6. T. D. Ladd, et al., Nature 464, 45 (2010).
7. Thompson, M.G. Politi, A., Matthews, J.C.F. & O’Brien, J.L. IET Circ. Devices Syst. 5, 94-102 (2011)
8. Reed, G. T., Mashanovich, G., Gardes, F. Y. & Thomson, D. J. Nature Photon. 4, 518-526 (2014).
9. Pernice, W. H. P. et al., Nat. commun. 3, 1325 (2012).
10. Silverstone, J. W., et al., Nature Photon. 8, 104-108 (2014).
11. Langford, N.K. et al., Nature 478, 360-363 (2011).
12. A. Elitzur and L. Vaidman, Found. Phys. 23, 987 (1993).
13. P. Kwiat, H. Weinfurter, T. Herzog, A. Zeilinger and M. A. Kasevich, Phys. Rev. Lett. 74, 4763 (1995).
14. P. Kwiat, et al., Phys. Rev. Lett. 83, 4725 (1999).
15. X. Ma, X. Guo, C. Schuck, K. Y. Fong, L. Jiang and H.X. Tang, Phys. Rev. A 90, 042109 (2014).
16. C. Schuck, X. Guo, L. R. Fan, X. Ma and H.X. Tang, Submitted (2015).
Quantum physics allows many fascinating and counter-intuitive phenomenon, which are fundamentally different to our daily life experience. Quantum technology enhanced information processing holds the promises to provide exponential speed-up in computation and unconditional communication security [1]. Photon, the quanta of light, is one of the nature quantum information carriers because photon travels in the speed of light and has excellent coherence property. There have been many experimental successes in the field of quantum optics. The majority of these experiments use bulk optical elements to build optical network for performing quantum information processing tasks [2-6]. Although these demonstrations are remarkable milestones in the development of experimental photonic quantum information processing, a full-scale optical quantum information processor would require much more complicated optical network. This type of optical network requires complex optical interferometers with high-level Interferometric stability, which is a significant challenge for traditional bulk optical elements. Integrated photonics [7] provides an ideal platform for tackling this challenging task. By using well-developed lithographic techniques developed in micro- and nano-fabrication industry, one can define the on-chip photonic structures, such as waveguides, directional couplers and so on for manipulating photonic qubits. The integrated photonic platform offers excellent Interferometric phase stability and perfect mode overlapping, which are necessary for high-fidelity qubit operations.
In this project, we focus on integrated quantum Silicon photonics, which is one of the leading candidates for realizing scalable quantum information processing due to the following reasons: 1. Silicon photonics fabrication techniques are well-established in the semiconductor industry and is scalable solution with high-level device integration. The footprint of the photonic device will not only much smaller than traditional bulk optical elements, but even comparing to the recently developed photonic devices based on glass, the silicon device dimensions are at least 50 times smaller (see Fig. 1). 2. High-speed silicon optical modulators are available [8]. 3. Single-photon superconducting detectors can be integrated onto the optical waveguides made by silicon [9]. This enables high-speed and high-efficiency single-photon detection. 4. Nonlinear optical properties of silicon and other CMOS compatible material are the resources for generating photon pairs [10] and could be employed for achieving deterministic two-photon gates via coherent photon conversion [11].
Within this project, we have successfully demonstrated the following crucial components with integrated quantum silicon photonics. 1. We have demonstrated an on-chip realization of the interaction-free measurement (IFM) based on silicon photonics. An IFM harnesses the wave-particle duality of single photons to sense the presence of an object via the modification of the interference pattern, which can be accomplished even if the photon and the object haven't interacted with each other [12]. By using the quantum Zeno effect, the efficiency of an IFM can be made arbitrarily close to unity [13-14]. To implement this idea, it requires precise control in fabricating the directional couplers with designed splitting ratios for making cascade interferometers. We use coupled-mode theory to numerically simulated, designed and fabricated various directional couplers. Experimentally, we exploit the inherent advantages of the lithographically written waveguides: excellent interferometric phase stability and mode matching, and obtain multipath interference with visibility above 98%. We achieved a normalized IFM efficiency up to 68.2%, which exceeds the 50% limit of the original IFM proposal [12].
2. We develop a hybrid superconducting-photonic circuit system to show how two of its main ingredients, quantum interference and single-photon detectors, can be combined in a scalable fashion on a silicon chip [16]. We demonstrate the suitability of this approach for integrated quantum optics by interfering and detecting photon pairs directly on the chip with waveguide-coupled single-photon detectors. Using a directional coupler implemented with silicon nitride nanophotonic waveguides, we observe 97% interference visibility when measuring photon statistics with two monolithically integrated superconducting single photon detectors. The photonic circuit and detector processing are compatible with standard semiconductor thin-film technology, making it possible to implement more complex and larger scale quantum photonic circuits on silicon chips.
Figure 1. Novel opportunities for photonic quantum information processing. Free space (bulk optics), glass-, Si-chip.
References:
1. M. A. Nielsen and I. L. Chuang, Quantum computation and quantum information (Cambridge University press, Cambridge, 2000).
2. J. L. O’Brien, Science 318, 1567 (2007).
3. P. Kok, et al., Rev. Mod. Phys. 79, 135 (2007).
4. J.-W. Pan, Z.-B. Chen, M. Zukowski, H. Weinfurter, and A. Zeilinger, Rev. Mod. Phys. 84, 777 (2012).
5. J. L. O’Brien, A. Furusawa, J. Vuckovic, Nat. Photon 3, 687 (2009).
6. T. D. Ladd, et al., Nature 464, 45 (2010).
7. Thompson, M.G. Politi, A., Matthews, J.C.F. & O’Brien, J.L. IET Circ. Devices Syst. 5, 94-102 (2011)
8. Reed, G. T., Mashanovich, G., Gardes, F. Y. & Thomson, D. J. Nature Photon. 4, 518-526 (2014).
9. Pernice, W. H. P. et al., Nat. commun. 3, 1325 (2012).
10. Silverstone, J. W., et al., Nature Photon. 8, 104-108 (2014).
11. Langford, N.K. et al., Nature 478, 360-363 (2011).
12. A. Elitzur and L. Vaidman, Found. Phys. 23, 987 (1993).
13. P. Kwiat, H. Weinfurter, T. Herzog, A. Zeilinger and M. A. Kasevich, Phys. Rev. Lett. 74, 4763 (1995).
14. P. Kwiat, et al., Phys. Rev. Lett. 83, 4725 (1999).
15. X. Ma, X. Guo, C. Schuck, K. Y. Fong, L. Jiang and H.X. Tang, Phys. Rev. A 90, 042109 (2014).
16. C. Schuck, X. Guo, L. R. Fan, X. Ma and H.X. Tang, Submitted (2015).