P13 - Photonic Quantum Computing

Philip Walther


Single photons provide unique advantages for quantum information applications due to their robustness, individual addressability and bosonic character. Moreover, the intrinsic mobility of single photons makes them the best quantum information carriers for quantum networks, delegated quantum cloud computing [R13-1] and novel quantum computation schemes such as Boson Sampling and quantum random walks [R13-2].

The long-term goals of our project are the development of quantum photonics technology for (i) secure delegated quantum computing in real-life scenarios and quantum homomorphic encryption schemes that enable a broad class of quantum computation on encrypted data, and (ii) hybrid quantum-classical systems, where classical computation is supported by feasible quantum photonics technology, and (iii) implementing machine learning and random-walk computations using complex integrated network structures, and (iv) demonstrating novel quantum protocols that exploit superimposed orders of gates for outperforming standard, fixed-order schemes.

PI Philip Walther on
Photonic Quantum Computing


Subproject Leader: Philip Walther

Co-PIs: Lee Rozema, Iris Agresti

PhD Students: Michael Antesberger, Daniel Kun

Master Students: Carla Richter, Mariana Schmid


Robust excitation of C-band quantum dots for quantum communication

M. Vyvlecka, L. Jehle, C. Nawrath, F. Giorgino, M. Bozzio, R. Sittig, M. Jetter, S. L. Portalupi, P. Michler, P. Walther

Applied Physics Letters 123, 174001 (2023)


Single-active-element demultiplexed multi-photon source

L. M. Hansen, L. Carosini, L. Jehle, F. Giorgino, R. Houvenaghel, M. Vyvlecka, J. C. Loredo, P. Walther

Optica Quantum 1, 1-5 (2023)


Demonstration of a Quantum Switch in a Sagnac Configuration

T. Strömberg, P. Schiansky, R. W. Peterson, M. T. Quintino, P. Walther

Physical Review Letters 131, 060803 (2023)


Demonstration of quantum-digital payments

P. Schiansky, J. Kalb, E. Sztatecsny, M.-C. Roehsner, T. Guggemos, A. Trenti, M. Bozzio, P. Walther

Nature Communications 14, 3849 (2023)


Nonlinear quantum logic with colliding graphene plasmons

G. Calajo, P. K. Jenke, L. A. Rozema, P. Walther, D. E. Chang, J. D. Cox

Physical Review Research 5, 031188 (2023)


Experimental higher-order interference in a nonlinear triple slit

P. Namdar, P. K. Jenke, I. Alonso Calafell, A. Trenti, M. Radonjic, B. Dakic, P. Walther, L. A. Rozema

Physical Review A 107, 032211 (2023)


Demonstration of universal time-reversal for qubit processes

P. Schiansky, T. Strömberg, D.- Trillo, V. Saggio, B. Dive, M. Navascues, P. Walther

Optica 10, 200-205 (2023)


Experimental Semi-quantum Key Distribution with Classical Users

F. Massa, P. Yadav, A. Moqanaki, W. O. Kravec, P. Mateusm N. Paunkovic, A. Souto, P. Walther

Quantum 6, 819 (2022)


Enhanced Photonic Maxwell’s Demon with Correlated Baths

G. L. Zanin, M. Antesberger, M. J. Jaquet, P. H. Souto Ribeiro, L. A. Rozema, P. Walther

Quantum 6, 810 (2022)


High-Harmonic Generation Enhancement with Graphene Heterostructures

A. Alonso, L. A. Rozema, A. Trenti, J. Bohn, E. J. C. Dias, P. K. Jenke, K. S. Menghrajani, D. Alcaraz Iranzo, F. J. Garcia de Abajo, F. H. L. Koppens, E. Hendry, P. Walther

Advanced Optical Materials (2022)


Few-Copy Entanglement Detection in the Presence of Noise

V. Saggio, P. Walther

Annalen der Physik 534, 7 (2022)


Enhancing quantum cryptography with quantum dot single-photon sources
M. Bozzio, M. Vyvlecka, M. Cosacchi, C. Nawrath, T. Seidelmann, J. C. Loredo, S. L. Portalupi, V. M. Axt, P. Michler, P. Walther
npj Quantum Information (2022)

Experimental entanglement of temporal order
G. Rubino, L. A. Rozema, F. Massa, M. Araujo, M. Zych, C. Brukner, P. Walther
Quantum 6, 621 (2022)

Measuring space-time curvature using maximally path-entangled quantum states
T. Mieling, C. Hilweg, P. Walther
Advanced Optical Materials (2022)

A perspective on few-copy entanglement detection in experiments
V. Saggio, P. Walther
Annalen der Physik (in print) (2022)

Inferring work by quantum superposing forward and time-reversal evolutions
G. Rubino, G. Manzano, L. A. Rozema, P. Walther, J. M. R. Parrondo, C. Brukner
Physical Review Research 4, 013208 (2022)

Experimental photonic quantum memristor
M. Spagnolo, J. Morris, S. Piacentini, M. Antesberger, F. Massa, A. Crespi, F. Ceccarelli, R. Osellame, P. Walther
Nature Photonics 16, 318–323 (2022)

Experimental quantum speed-up in reinforcement learning agents
V. Saggio, B.E. Asenbeck, A. Hamann, T. Strömberg, P. Schiansky, V. Dunjko, N. Friis, N.C. Harris, M. Hochberg, D. Englund, S. Wölk, H. J. Briegel, P. Walther
Nature 591, 229–233 (2021)

Experimental quantum communication enhancement by superposing trajectories
G. Rubino, L. A. Rozema, D. Ebler, H. Kristjánsson, S. Salek, P. A. Guérin, A. A. Abbott, C. Branciard, Č. Brukner, G. Chiribella, P. Walther
Phys. Rev. Research 3, 013093 (2021)

Experimental Quantum Homomorphic Encryption
J. Zeuner,I. Pitsios, SH. Tan, A. Sharma, J. Fizsimons, R. Osellame and P. Walther
npj Quantum Information 7, 25 (2021)

Giant enhancement of third-harmonic generation in graphene–metal heterostructures
I. Alonso Calafell, L.A. Rozema, D. Alcaraz Iranzo, A. Trenti, P.K. Jenke, J.D. Cox, A. Kumar, H. Bieliaiev, S. Nanot, C. Peng, D.K. Efetov, J.Y. Hong, J. Kong, D.R. Englund, F.J. García de Abajo, F.H.L. Koppens, P. Walther
Nature Nanotechnology 16, 318–324 (2021)

Cross-Verification of Independent Quantum Devices
C. Greganti, T. F. Demarie, M. Ringbauer, J. A. Jones, V. Saggio, I. Alonso Calafell, L. A. Rozema, A. Erhard, M. Meth, L. Postler, R. Stricker, P. Schindler, R. Blatt, T. Monz, P. Walther, J. F. Fitzsimons
Physical Review X 11, 031049 (2021)

Probabilistic one-time programs using quantum entanglement
M.-C. Röhsner, J. A. Kettlewell, J. Fitzsimons, P. Walther
npj Quantum Information 7, 98 (2021)

Quantum cryptography with highly entangled photons from semiconductor quantum dots
C. Schimpf, M. Reindl, D. Huber, B. Lehner, S.F. Covre Da Silva, S. Manna, M. Vyvlecka, P. Walther, A. Rastelli
Science Advances 7, 16 (2021)

Fiber-compatible photonic feed-forward with 99% fidelity
G. L. Zanin, M. Jacquet, M. Spagnolo, P. Schiansky, I. Alonso Calafell, L.A. Rozema, P. Walther
Optic Express 29, 3425-3437 (2021)

Quantum superposition of thermodynamic evolutions with opposing time’s arrows
G. Rubino, G. Manzano, Č. Brukner
Communication Physics 4, 251 (2021)

Communication through quantum-controlled noise
P. A. Guérin, G. Rubino, Č. Brukner
Phys. Rev. A 99, 062317 (2019)

Quantum computing with graphene plasmons
I. A. Calafell, J. D. Cox, M. Radonjic, J. R. M. Saavedra, F. J. Garcia de Abajo, L. A. Rozema, P. Walther
npj Quantum Information, 5, 37 (2019)

Experimental few-copy multipartite entanglement detection
V. Saggio, A. Dimić, C. Greganti, L. A. Rozema, P. Walther, B. Dakić
Nature Physics 15 (2019)

Experimental Two‐Way Communication with One Photon
F. Massa, A. Moqanaki, Ä. Baumeler, F. Del Santo, J. A. Kettlewell, B. Dakić, P. Walther
Advanced Quantum Technologies (2019)

Trace-free counterfactual communication with a nanophotonic processor
I. Alonso Calafell, T. Strömberg, D. R. M. Arvidsson-Shukur, L. A. Rozema, V. Saggio, C. Greganti, N. C. Harris, M. Prabhu, J. Carolan, M. Hochberg, T. Baehr-Jones, D. Englund, C. H. W. Barnes, P. Walther
npj Quantum Information 5, 61 (2019)



High-harmonic generation enhancement with graphene heterostructures
I. A. Alonso, L. A. Rozema, A. Trenti, J. Bohn, E. J. C. Dias, P. K. Jenke, K. S. Menghrajani, D. Alcaraz Iranzo, F. J. Garcia de Abajo, F. H. L. Koppens, E. Hendry, P. Walther
preprint arXiv:2203.14644v1 [con-mat.mes-hall] (2022)

Experimental semi-device-independent certification of indefinite causal order
H. Cao, J. Bavaresco, N.-N. Wang, L. A. Rozema, C. Zhang, Y.-F. Huang, B.-H. Liu, C.-F. Li, G.-C. Guo, P. Walther
preprint arXiv:2202.05346 [quant-ph] (2022)

Experimental Higher-Order Interference in a Nonlinear Triple Slit
P. Namdar, P. K. Jenke, I. Alonso Calafell, A. Trenti, M. Radonjic, B. Dakic, P. Walther, L. A. Rozema
preprint arXiv:2112.06965 [quant-ph] (2021)

Enhanced Photonic Maxwell's Demon with Correlated Baths
G. L. Zanin, M. Antesberger, M. J. Jacquet, P. H. Souto Ribeiro, L. A. Rozema, P. Walther
preprint arXiv:2107.09686 [quant-ph] (2021)


For further publications: see here.