### Abstract

The efficient transfer of a quantum state from photons to matter qubits in order to momentarily store information has become a central problem in quantum information processing. A quantum memory turns out to be an essential tool to achieve advanced technologies such as quantum networks, quantum repeaters, deterministic single photon sources or linear optics quantum computers. The realization of a quantum interface has been investigated in various forms, among which one can find solid-state atomic ensembles, color centers in crystal lattices, cold atomic gases, optical phonons in diamond and many others. Here we focus on a broadband quantum interface for high repetition rate (76 MHz) ultrafast optical pulses (250 fs) at telecommunication wavelength (1530 nm) based on the photon echo process occurring in semiconductor quantum dots. We evaluated the quantum state of photonic qubits in order to characterize the impact of the storage on the transmitted signal. Homodyne traces corresponding to projections of the Wigner function of the signal on rotated quadrature components were obtained using broadband balanced homodyne detection, i.e. mixing the ultrafast optical pulses to analyze with a high repetition rate pulsed local oscillator. The reconstruction of the Wigner function from the homodyne traces was performed using three algorithms: The inverse Radon transform, the minimax adaptive reconstruction and the maximum likelihood estimation. The three methods lead to similar results, concluding that for an input pulse in a coherent state, the reemitted photon echo is also in a coherent state.

Original language | English |
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Title of host publication | Advances in Photonics of Quantum Computing, Memory, and Communication XII |

Editors | Zameer Ul Hasan, Philip R. Hemmer, Alan L. Migdall |

Publisher | SPIE |

ISBN (Electronic) | 9781510625082 |

DOIs | |

Publication status | Published - 2019 Jan 1 |

Event | Advances in Photonics of Quantum Computing, Memory, and Communication XII 2019 - San Francisco, United States Duration: 2019 Feb 5 → 2019 Feb 7 |

### Publication series

Name | Proceedings of SPIE - The International Society for Optical Engineering |
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Volume | 10933 |

ISSN (Print) | 0277-786X |

ISSN (Electronic) | 1996-756X |

### Conference

Conference | Advances in Photonics of Quantum Computing, Memory, and Communication XII 2019 |
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Country | United States |

City | San Francisco |

Period | 19/2/5 → 19/2/7 |

### Fingerprint

### Keywords

- broadband quantum interface
- inverse Radon transform
- maximum likelihood estimation
- minimax algorithm
- photon echo
- Quantum state tomography
- telecommunication wavelength
- ultrafast optical pulses

### ASJC Scopus subject areas

- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Computer Science Applications
- Applied Mathematics
- Electrical and Electronic Engineering

### Cite this

*Advances in Photonics of Quantum Computing, Memory, and Communication XII*[109330V] (Proceedings of SPIE - The International Society for Optical Engineering; Vol. 10933). SPIE. https://doi.org/10.1117/12.2507827

**Quantum state tomography of ultrafast optical pulses at telecom wavelength by broadband balanced homodyne detection.** / Blésin, Terence; Matsushita, Rei; Akahane, Kouichi; Hayase, Junko.

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

*Advances in Photonics of Quantum Computing, Memory, and Communication XII.*, 109330V, Proceedings of SPIE - The International Society for Optical Engineering, vol. 10933, SPIE, Advances in Photonics of Quantum Computing, Memory, and Communication XII 2019, San Francisco, United States, 19/2/5. https://doi.org/10.1117/12.2507827

}

TY - GEN

T1 - Quantum state tomography of ultrafast optical pulses at telecom wavelength by broadband balanced homodyne detection

AU - Blésin, Terence

AU - Matsushita, Rei

AU - Akahane, Kouichi

AU - Hayase, Junko

PY - 2019/1/1

Y1 - 2019/1/1

N2 - The efficient transfer of a quantum state from photons to matter qubits in order to momentarily store information has become a central problem in quantum information processing. A quantum memory turns out to be an essential tool to achieve advanced technologies such as quantum networks, quantum repeaters, deterministic single photon sources or linear optics quantum computers. The realization of a quantum interface has been investigated in various forms, among which one can find solid-state atomic ensembles, color centers in crystal lattices, cold atomic gases, optical phonons in diamond and many others. Here we focus on a broadband quantum interface for high repetition rate (76 MHz) ultrafast optical pulses (250 fs) at telecommunication wavelength (1530 nm) based on the photon echo process occurring in semiconductor quantum dots. We evaluated the quantum state of photonic qubits in order to characterize the impact of the storage on the transmitted signal. Homodyne traces corresponding to projections of the Wigner function of the signal on rotated quadrature components were obtained using broadband balanced homodyne detection, i.e. mixing the ultrafast optical pulses to analyze with a high repetition rate pulsed local oscillator. The reconstruction of the Wigner function from the homodyne traces was performed using three algorithms: The inverse Radon transform, the minimax adaptive reconstruction and the maximum likelihood estimation. The three methods lead to similar results, concluding that for an input pulse in a coherent state, the reemitted photon echo is also in a coherent state.

AB - The efficient transfer of a quantum state from photons to matter qubits in order to momentarily store information has become a central problem in quantum information processing. A quantum memory turns out to be an essential tool to achieve advanced technologies such as quantum networks, quantum repeaters, deterministic single photon sources or linear optics quantum computers. The realization of a quantum interface has been investigated in various forms, among which one can find solid-state atomic ensembles, color centers in crystal lattices, cold atomic gases, optical phonons in diamond and many others. Here we focus on a broadband quantum interface for high repetition rate (76 MHz) ultrafast optical pulses (250 fs) at telecommunication wavelength (1530 nm) based on the photon echo process occurring in semiconductor quantum dots. We evaluated the quantum state of photonic qubits in order to characterize the impact of the storage on the transmitted signal. Homodyne traces corresponding to projections of the Wigner function of the signal on rotated quadrature components were obtained using broadband balanced homodyne detection, i.e. mixing the ultrafast optical pulses to analyze with a high repetition rate pulsed local oscillator. The reconstruction of the Wigner function from the homodyne traces was performed using three algorithms: The inverse Radon transform, the minimax adaptive reconstruction and the maximum likelihood estimation. The three methods lead to similar results, concluding that for an input pulse in a coherent state, the reemitted photon echo is also in a coherent state.

KW - broadband quantum interface

KW - inverse Radon transform

KW - maximum likelihood estimation

KW - minimax algorithm

KW - photon echo

KW - Quantum state tomography

KW - telecommunication wavelength

KW - ultrafast optical pulses

UR - http://www.scopus.com/inward/record.url?scp=85068005566&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85068005566&partnerID=8YFLogxK

U2 - 10.1117/12.2507827

DO - 10.1117/12.2507827

M3 - Conference contribution

AN - SCOPUS:85068005566

T3 - Proceedings of SPIE - The International Society for Optical Engineering

BT - Advances in Photonics of Quantum Computing, Memory, and Communication XII

A2 - Ul Hasan, Zameer

A2 - Hemmer, Philip R.

A2 - Migdall, Alan L.

PB - SPIE

ER -