Abstract
That two photons pass each other undisturbed in free space is ideal for the faithful transmission of information, but prohibits an interaction between the photons. Such an interaction is, however, required for a plethora of applications in optical quantum information processing1. The long-standing challenge here is to realize a deterministic photon–photon gate, that is, a mutually controlled logic operation on the quantum states of the photons. This requires an interaction so strong that each of the two photons can shift the other’s phase by π radians. For polarization qubits, this amounts to the conditional flipping of one photon’s polarization to an orthogonal state. So far, only probabilistic gates2 based on linear optics and photon detectors have been realized3, because “no known or foreseen material has an optical nonlinearity strong enough to implement this conditional phase shift”4. Meanwhile, tremendous progress in the development of quantum-nonlinear systems has opened up new possibilities for single-photon experiments5. Platforms range from Rydberg blockade in atomic ensembles6 to single-atom cavity quantum electrodynamics7. Applications such as single-photon switches8 and transistors9,10, two-photon gateways11, nondestructive photon detectors12, photon routers13 and nonlinear phase shifters14,15,16,17,18 have been demonstrated, but none of them with the ideal information carriers: optical qubits in discriminable modes. Here we use the strong light–matter coupling provided by a single atom in a high-finesse optical resonator to realize the Duan–Kimble protocol19 of a universal controlled phase flip (π phase shift) photon–photon quantum gate. We achieve an average gate fidelity of (76.2 ± 3.6) per cent and specifically demonstrate the capability of conditional polarization flipping as well as entanglement generation between independent input photons. This photon–photon quantum gate is a universal quantum logic element, and therefore could perform most existing two-photon operations. The demonstrated feasibility of deterministic protocols for the optical processing of quantum information could lead to new applications in which photons are essential, especially long-distance quantum communication and scalable quantum computing.
This is a preview of subscription content, access via your institution
Access options
Subscribe to this journal
Receive 51 print issues and online access
$199.00 per year
only $3.90 per issue
Buy this article
- Purchase on Springer Link
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
References
Kok, P. & Lovett, B. W. Introduction to Optical Quantum Information Processing (Cambridge Univ. Press, 2010)
Knill, E., Laflamme, R. & Milburn, G. J. A scheme for efficient quantum computation with linear optics. Nature 409, 46–52 (2001)
O’Brien, J. L., Pryde, G. J., White, A. G., Ralph, T. C. & Branning, D. Demonstration of an all-optical quantum controlled-NOT gate. Nature 426, 264–267 (2003)
O’Brien, J. L. Optical quantum computing. Science 318, 1567–1570 (2007)
Chang, D. E., Vuletić, V. & Lukin, M. D. Quantum nonlinear optics—photon by photon. Nat. Photon. 8, 685–694 (2014)
Gorshkov, A. V., Otterbach, J., Fleischhauer, M., Pohl, T. & Lukin, M. D. Photon-photon interactions via Rydberg blockade. Phys. Rev. Lett. 107, 133602 (2011)
Reiserer, A. & Rempe, G. Cavity-based quantum networks with single atoms and optical photons. Rev. Mod. Phys. 87, 1379–1418 (2015)
Baur, S., Tiarks, D., Rempe, G. & Dürr, S. Single-photon switch based on Rydberg blockade. Phys. Rev. Lett. 112, 073901 (2014)
Tiarks, D., Baur, S., Schneider, K., Dürr, S. & Rempe, G. Single-photon transistor using a Förster resonance. Phys. Rev. Lett. 113, 053602 (2014)
Gorniaczyk, H., Tresp, C., Schmidt, J., Fedder, H. & Hofferberth, S. Single-photon transistor mediated by interstate Rydberg interactions. Phys. Rev. Lett. 113, 053601 (2014)
Kubanek, A. et al. Two-photon gateway in one-atom cavity quantum electrodynamics. Phys. Rev. Lett. 101, 203602 (2008)
Reiserer, A., Ritter, S. & Rempe, G. Nondestructive detection of an optical photon. Science 342, 1349–1351 (2013)
Shomroni, I. et al. All-optical routing of single photons by a one-atom switch controlled by a single photon. Science 345, 903–906 (2014)
Turchette, Q. A., Hood, C. J., Lange, W., Mabuchi, H. & Kimble, H. J. Measurement of conditional phase shifts for quantum logic. Phys. Rev. Lett. 75, 4710–4713 (1995)
Tiecke, T. G. et al. Nanophotonic quantum phase switch with a single atom. Nature 508, 241–244 (2014)
Volz, J., Scheucher, M., Junge, C. & Rauschenbeutel, A. Nonlinear π phase shift for single fibre-guided photons interacting with a single resonator-enhanced atom. Nat. Photon. 8, 965–970 (2014)
Beck, K. M., Hosseini, M., Duan, Y. & Vuletić, V. Large conditional single-photon cross-phase modulation. Preprint at https://arxiv.org/abs/1512.02166 (2015)
Tiarks, D., Schmidt, S., Rempe, G. & Dürr, S. Optical π phase shift created with a single-photon pulse. Sci. Adv. 2, e1600036 (2016)
Duan, L.-M. & Kimble, H. J. Scalable photonic quantum computation through cavity-assisted interactions. Phys. Rev. Lett. 92, 127902 (2004)
Shapiro, J. H. Single-photon Kerr nonlinearities do not help quantum computation. Phys. Rev. A 73, 062305 (2006)
Gea-Banacloche, J. Impossibility of large phase shifts via the giant Kerr effect with single-photon wave packets. Phys. Rev. A 81, 043823 (2010)
Reiserer, A., Kalb, N., Rempe, G. & Ritter, S. A quantum gate between a flying optical photon and a single trapped atom. Nature 508, 237–240 (2014)
Duan, L.-M., Wang, B. & Kimble, H. J. Robust quantum gates on neutral atoms with cavity-assisted photon scattering. Phys. Rev. A 72, 032333 (2005)
Reiserer, A., Nölleke, C., Ritter, S. & Rempe, G. Ground-state cooling of a single atom at the center of an optical cavity. Phys. Rev. Lett. 110, 223003 (2013)
Poyatos, J. F., Cirac, J. I. & Zoller, P. Complete characterization of a quantum process: the two-bit quantum gate. Phys. Rev. Lett. 78, 390–393 (1997)
Bagan, E., Baig, M. & Muñoz-Tapia, R. Minimal measurements of the gate fidelity of a qudit map. Phys. Rev. A 67, 014303 (2003)
Uphoff, M., Brekenfeld, M., Rempe, G. & Ritter, S. Frequency splitting of polarization eigenmodes in microscopic Fabry-Perot cavities. New J. Phys. 17, 013053 (2015)
Briegel, H.-J., Dür, W., Cirac, J. I. & Zoller, P. Quantum repeaters: the role of imperfect local operations in quantum communication. Phys. Rev. Lett. 81, 5932–5935 (1998)
Raussendorf, R. & Briegel, H. J. A one-way quantum computer. Phys. Rev. Lett. 86, 5188–5191 (2001)
Ladd, T. D. et al. Quantum computers. Nature 464, 45–53 (2010)
Acknowledgements
We thank N. Kalb, A. Neuzner, A. Reiserer and M. Uphoff for discussions and support throughout the experiment. This work was supported by the European Union (Collaborative Project SIQS) and by the Bundesministerium für Bildung und Forschung via IKT 2020 (Q.com-Q) and by the Deutsche Forschungsgemeinschaft via the excellence cluster Nanosystems Initiative Munich (NIM). S.W. was supported by the doctorate programme Exploring Quantum Matter (ExQM).
Author information
Authors and Affiliations
Contributions
All authors contributed to the experiment, the analysis of the results and the writing of the manuscript.
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing financial interests.
Extended data figures and tables
Extended Data Figure 1 Ramsey-like spectrum to calibrate the atomic state rotations.
After initialization of the atom in |↑〉, we perform the same sequence of three Raman pulses as in the gate protocol. The final population in |↑〉 is determined as a function of the two-photon detuning of the employed Raman pair with respect to the frequency difference between the two atomic qubit states. The solid dots are measured data with statistical error bars (standard error of the mean). The solid line is the fit of a theoretical model based on the sequence of rotations. It yields results for the Rabi frequency of the atomic spin rotation, an offset of the two-photon detuning, as for example, induced by ambient magnetic fields, and the light shift imposed by the Raman laser pair, all with ±3 kHz precision.
Rights and permissions
About this article
Cite this article
Hacker, B., Welte, S., Rempe, G. et al. A photon–photon quantum gate based on a single atom in an optical resonator. Nature 536, 193–196 (2016). https://doi.org/10.1038/nature18592
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/nature18592
This article is cited by
-
Giant optical polarisation rotations induced by a single quantum dot spin
Nature Communications (2024)
-
A subwavelength atomic array switched by a single Rydberg atom
Nature Physics (2023)
-
Non-linear Boson Sampling
npj Quantum Information (2023)
-
Brillouin zone folding driven bound states in the continuum
Nature Communications (2023)
-
On-chip spin-photon entanglement based on photon-scattering of a quantum dot
npj Quantum Information (2023)
Comments
By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.