Juan Rafael Alvarez
Juan Rafael Alvarez

Assistant Professor (Enseignant Chercheur)

Telecom Paris

About Me

I am a physicist interested in understanding quantum optical phenomena, especially through experiments that involve the use of light and matter. I am currently an assistant professor (maître de conférences) in the Optical Telecommunications Group (GTO) at Telecom Paris. Before this, I was a postdoctoral researcher at the Centre de Nanosciences et Nanotechnologies (C2N) of the CNRS in Palaiseau, France, I graduated from a DPhil in Atomic and Laser Physics at the University of Oxford, and have performed a masters degree in Marseille and Barcelona, and Physics and Mathematics undergraduates at the Universidad de los Andes, in Bogotá, Colombia. I have also been a teacher, a scientific disseminator, and have made part of several associations to promote the knowledge of optics, photonics and quantum technologies.

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Interests
  • Quantum Optics
  • Quantum Communications
  • Atomic Physics
  • Cavity QED
  • Nanophotonics
  • Random number generation
Education

  • PhD Atomic and Laser Physics

    University of Oxford

  • Europhotonics Master

    Aix-Marseille Université - Photonics BCN

  • Bachelor of Mathematics

    Universidad de los Andes Colombia

  • Bachelor of Physics

    Universidad de los Andes Colombia

Featured Publications
Decoherence assisted quantum key distribution
Measuring Wigner functions of quantum states of light in the undergraduate lab

Measuring Wigner functions of quantum states of light in the undergraduate lab

We present an educational activity for measuring Wigner distribution functions of quantum states of light in the undergraduate laboratory. The activity was implemented by undergraduate students in different courses of the undergraduate curriculum, and the resulting activity was tested by different students of an introductory Quantum Optics course at the Universidad de los Andes in Bogotá, Colombia. The activity consists of a two-hour laboratory practice where students work in a pre-aligned experimental setup and then use an open-access, custom made computational graphical user interface that enables the reconstruction of the Wigner distribution function. Since the testing of the activity coincided with the COVID-19 pandemic, the possibility of analyzing simulated data was included in the computational user interface. The activity is now running for in-person classes and its virtual feature is now valuable for the implementation of distance learning of Quantum Optics.

How to administer an antidote to Schrödinger's cat
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How to administer an antidote to Schrödinger's cat

In his 1935 Gedankenexperiment, Erwin Schrödinger imagined a poisonous substance which has a 50% probability of being released, based on the decay of a radioactive atom. As such, the life of the cat and the state of the poison become entangled, and the fate of the cat is determined upon opening the box. We present an experimental technique that keeps the cat alive on any account. This method relies on the time-resolved Hong-Ou-Mandel effect: two long, identical photons impinging on a beam splitter always bunch in either of the outputs. Interpreting the first photon detection as the state of the poison, the second photon is identified as the state of the cat. Even after the collapse of the first photon’s state, we show their fates are intertwined through quantum interference. We demonstrate this by a sudden phase change between the inputs, administered conditionally on the outcome of the first detection, which steers the second photon to a pre-defined output and ensures that the cat is always observed alive.

Random number generation by coherent detection of quantum phase noise
QRNG

Random number generation by coherent detection of quantum phase noise

‘In 2010 Qi et al. [Opt. Lett. 35(3), 312 (2010)] demonstrated a random number generator based on the drift of the phase of a laser due to spontaneous emission, The out-of-the-lab implementation of this scheme presents two main drawbacks: it requires a long and highly unbalanced interferometer to generate a random phase with uniform probability distribution, or alternatively, a shorter and slightly unbalanced interferometer that notwithstanding requires active stabilization and does not generate a uniform probability distribution without randomness extraction. Here we demonstrate that making use of the random nature of the phase difference between two independent laser sources and two coherent detectors we can overcome these limitations. The two main advantages of the system demonstrated are: i) it generates a probability distribution of quantum origin which is intrinsically uniform and thus in principle needs no randomness extraction for obtaining a uniform distribution, and ii) the phase is measured with telecom equipment routinely used for high capacity coherent optical communications. The speed of random bit generation is determined by the photodetector bandwidth and the linewidth of the lasers. As a by-product of our method, we have obtained images of how phase noise develops with time in a laser. This provides a highly visual alternative way of measuring the coherence time of a laser.’

Recent Publications
Astghik Saharyan, Juan Rafael Alvarez, Axel Kuhn, Stéphane Guérin (2024). Effective models for quantum optics with multilayer open cavities.
PDF Cite arXiv
Daniel R. Sabogal, Daniel F. Urrego, Juan Rafael Alvarez, Andrés F. Herrera, Juan P. Torres, Alejandra Valencia (2024). Decoherence assisted quantum key distribution.
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Juan Rafael Alvarez, Andrés Martínez Silva, Alejandra Valencia (2023). Measuring Wigner functions of quantum states of light in the undergraduate laboratory.
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Jan Ole Ernst, Juan Rafael Alvarez, Thomas D. Barrett, Axel Kuhn (2023). Bursts of polarised single photons from atom-cavity sources. In J. Phys. B.
Cite DOI Journal of Physics B: Atomic, Molecular and Optical Physics
Juan Rafael Alvarez, Andrés Martínez Silva, Alejandra Valencia (2023). Measuring Wigner functions of quantum states of light in the undergraduate lab. In ETOP 2023.
Cite DOI ETOP 2023
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