Sviluppo di sorgenti di luce quantistica

Quantum cryptography and quantum communication require the development of novel technologies to encode the qubit on-demand, for example, in the polarization state of a photon, and the possibility of obtaining particular quantum states of light as pairs of entangled photons. This demand is addressed through the development on one hand of single photon sources in the visible or near-infrared range for fiber quantum telecommunications, using for example quantum emitters coupled to phase change materials; on the other, generating pairs of entangled photons through the engineering of the nonlinear optical properties of dielectric metasurfaces capable of converting an input photon into two less energetic but entangled photons.
Among the studied topics:

• Single photon sources for quantum telecommunications
• Spontaneous parametric down-conversion in dielectric metasurfaces

Contacts: Tiziana Cesca, Giovanni Mattei
Sito web: https://materia.dfa.unipd.it/nsg/

  Realization of an experimental apparatus for ion trapping

We are currently working on a new experimental apparatus dedicated to the trapping and control of Barium ions, an atomic species of growing interest in the field of quantum technologies.
The experiment aims to achieve coherent control of the electronic and motional state of a string of trapped ions, to be used as a platform for quantum simulations and computations. The main areas of technological research include: the design and realization of the ion trap by glass microfabrication, the use of cryogenic technologies in the experimental apparatus, and the use of integrated photonics for laser light delivery and ion control.
Contacts: Carmelo Mordini

  Control of multilevel systems (qudit) with photonic technologies

The complex structure of the electronic states of trapped atoms and ions makes it possible to extend current quantum computation paradigms from two-level control - qubits - to multilevel schemes called qudits. In our group we explore new methods of atomic qudit control, enabled by the use of photonic technologies and optical metamaterials. This research area is developed in collaboration with the experimental Metasurfaces group (Prof. Romanato) and the Quantum Matter and Information theoretical group (Prof. Montangero).
Contacts: Carmelo Mordini

  High-dimensional Quantum Key Distribution

Quantum key distribution (QKD) protocols provide a method for exchanging an encryption key between two parties, the security of which is guaranteed by the unbreakable laws of quantum mechanics. Research in the field of high-dimensional quantum key distribution is revolutionizing the cryptography and security landscape in both free-space and optical fiber communications. Traditionally, QKD protocols are based on qubits, defined in a 2-dimensional space and implemented with polarization states. Increasing the dimension of the Hilbert state space involves not only an increase in bits per photon, but also an improvement in robustness and resistance to attacks and noise. Research in this area focuses on the design, development, and test of compact and integrable optical devices for the generation and measurement of high-dimensional photonic states by controlling the spatial properties of light.
Contacts: Filippo Romanato, Gianluca Ruffato, Carmelo Mordini

  Innovative optics for ion trapping

Quantum computers require trapping and confinement capabilities with high levels of precision and versatility. Research in this area focuses on the design and integration of innovative optics in the form of metalenses. Compared to traditional optics, metalenses allow unprecedented manipulation of light through integrated, compact platforms with a high density of functionality. It is possible to create arrays of optical traps with customized spacing and geometries, while the manipulation of the polarization and spatial properties of light opens to the possibility of dynamic control with compact and efficient solutions. This allows for greater scalability and finer control of atomic interactions compared to traditional techniques. The ability to manipulate individual atoms with sub-micrometric precision paves the way for building more efficient and scalable quantum computers, where each trapped atom acts as a qubit in a complex lattice. This technology not only promises to overcome the limitations of current trapping techniques, but may also represent a significant step towards the practical realization of large-scale quantum computers.
Contacts: Filippo Romanato, Gianluca Ruffato

  High-dimensional photon entanglement

The exploitation of entangled photons is opening new frontiers of research and applications in several fields, from life sciences to information and communications technologies. For example, entangled photons are revolutionizing the field of optical microscopy in the so-called "ghost imaging" technique, where information about an object is reconstructed using correlation with photons that have never interacted directly with the object itself, an approach that can be extremely advantageous when direct access to the object is limited, and which also finds extensions in different fields (for example, LIDAR) and to beams of matter waves (electron microscopy). In the field of quantum cryptography and communication, pairs of entangled photons provide sources for quantum key distribution or for the realization of critical aspects such as the teleportation of quantum states at network nodes. In this area, the research focuses on the study, both theoretical and experimental, of high-dimensional photon entanglement on the spatial properties of photons, such as the orbital angular momentum, and on how to control the statistical distribution of these properties using optical elements integrated with the sources.
Contacts: Filippo Romanato, Gianluca Ruffato

  Quantum sensors

Quantum sensors are new devices whose measurement capability is enabled by our ability to manipulate and readout their quantum states. They have the potential to significantly improve the sensitivity of our lab-scale, tabletop experiments in fundamental physics, as for instance the detection of light Dark Matter (DM), or the measurement of electric dipole moments (EDM). In our laboratory, we apply transmon-based microwave photon counters to readout hybrid magnon-photon systems or plain 3D microwave resonators, respectively allowing to probe for interactions of hypothetical particles with fermions and photons. In addition, we focus on the development of cryocrystals of inert gases doped with polar molecules to improve the current precision of electron EDM measurements.
Contacts: Caterina Braggio