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CLAUDIO BONIZZONI

Ricercatore t.d. art. 24 c. 3 lett. A
Dipartimento di Scienze Fisiche, Informatiche e Matematiche sede ex-Fisica

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Pubblicazioni

2023 - Coherent Quantum Network of Superconducting Qubits as a Highly Sensitive Detector of Microwave Photons for Searching of Galactic Axions [Relazione in Atti di Convegno]
Gatti, C.; Affronte, M.; Balanov, A.; Bonizzoni, C.; Brida, G.; Chiariello, F.; Chikhi, N.; Coda, G.; D'Elia, A.; Gioacchino, D. Di; Enrico, E.; Eremin, I.; Ernajes, M.; Il'Ichev, E.; Fasolo, L.; Fistul, M.; Ghirri, A.; Greco, A.; Ligi, C.; Maccarone, G.; Meda, A.; Navez, P.; Oelsner, G.; Rajteri, M.; Rettaroli, A.; Ruggiero, B.; Savel'Ev, S.; Silvestrini, P.; Tocci, S.; Ustinov, A.; Vanacore, P.; Zagoskin, A.; Lisitskiy, M.
abstract

We propose a novel approach to detect a low power microwave signal with a frequency of the order of several GHz based on a coherent collective response of quantum states occurring in a superconducting qubits network (SQN). An SQN composes of a large number of superconducting qubits embedded in a low-dissipative superconducting resonator. Our theory predicts that an SQN interacting with the off-resonance microwave radiation, demonstrates the collective alternating current Stark effect that can be measured even in the limit of single photon counting. A design of the layout of three terminals SQN detectors containing 10 flux qubits weakly coupled to a low-dissipative R-resonator and T-transmission line was developed. The samples were fabricated by Al-based technology with Nb resonator. The SQN detector was tested in terms of microwave measurements of scattering parameters and two-tone spectroscopy. A substantial shift of the frequency position of the transmission coefficient drop induced by a second tone pump signal was observed, and this effect clearly manifests a nonlinear multiphoton interaction between the second-tone microwave pump signal and an array of qubits.

2023 - Coupling Sub-nanoliter BDPA Organic Radical Spin Ensembles with YBCO Inverse Anapole Resonators [Articolo su rivista]
Bonizzoni, Claudio; Maksutoglu, Maksut; Ghirri, Alberto; van Tol, John; Rameev, Bulat; Affronte, Marco
abstract

We report the development and test of planar microwave Inverse Anapole Resonators (IARs) made of superconducting Yttrium Barium Copper Oxide (YBCO) for electron spin resonance spectroscopy on small samples. We first characterize our resonators in zero field and then by carrying out transmission spectroscopy on a diluted α,γ-bisdiphenylene-β-phenylally (BDPA) organic radical spin ensemble in an applied magnetic field. These IARs allow us to carry out electron spin resonance spectroscopy both in continuous-wave and pulsed-wave mode, and to estimate the spin memory time of BDPA. The comparison with the results obtained for the same sample on typical linear coplanar resonators shows an improvement by ≈2 - up to3 – orders of magnitude in spin sensitivity, with effective sensing volumes below 1 nanoliter. The best sensitivity we achieved is S≈10^7 spin/(Hz)^1/2 in the pulsed-wave regime. These results compare well with similar experiments reported in the literature.

2023 - Ultrastrong Magnon-Photon Coupling Achieved by Magnetic Films in Contact with Superconducting Resonators [Articolo su rivista]
Ghirri, A.; Bonizzoni, C.; Maksutoglu, M.; Mercurio, A.; Di Stefano, O.; Savasta, S.; Affronte, M.
abstract

Coherent coupling between spin-wave excitations (magnons) and microwave photons in a cavity may disclose new paths to unconventional phenomena as well as novel applications. Here, we present a systematic investigation of yttrium iron garnets (YIG) films on top of coplanar waveguide resonators made of superconducting YBa2Cu3O7 (YBCO). We first show that spin-wave excitations with frequency higher than the Kittel mode can be excited by putting in direct contact a 5-pm-thick YIG film with the YBCO coplanar resonator (cavity frequency & omega;c/27r = 8.65 GHz). With this configuration, we obtain very large values of the collective coupling strength & lambda;/27r & AP; 2 GHz and cooperativity C = 5 x 104. Transmission spectra are analyzed by a modified Hopfield model for which we provide an exact solution that allows us to well reproduce spectra by introducing a limited number of free parameters. It turns out that the coupling of the dominant magnon mode with photons exceeds 0.2 times the cavity frequency, thus demonstrating the achievement of the ultrastrong-coupling regime with this architecture. Our analysis also shows a vanishing contribution of the diamagnetic term, which is a peculiarity of pure spin systems.

2022 - Machine-Learning-Assisted Manipulation and Readout of Molecular Spin Qubits [Articolo su rivista]
Bonizzoni, Claudio; Tincani, Mirco; Santanni, Fabio; Affronte, Marco
abstract

Machine learning finds application in the quantum control and readout of qubits. In this work we apply artificial neural networks to assist the manipulation and the readout of a prototypical molecular spin qubit-an oxovanadium(IV) moiety-in two experiments designed to test the amplitude and the phase recognition, respectively. We first successfully use an artificial network to analyze the output of a storage-retrieval protocol with four input pulses to recognize the echo positions and, with further post selection on the results, to infer the initial input pulse sequence. We then apply an artificial neural network to ascertain the phase of the experimentally measured Hahn echo, showing that it is possible to correctly detect its phase and to recognize additional single-pulse phase shifts added during manipulation.

2022 - Ultra-strong coupling in the hybrid quantum system consisting of planar MW resonator and YIG material [Relazione in Atti di Convegno]
Maksutoglu, M.; Ghirri, A.; Bonizzoni, C.; Cinar, K.; Yorulmaz, S. C.; Yildiz, F.; Affronte, M.; Rameev, B.
abstract

Ultra-strong coupling between inverse anapole resonator (IAR) and YIG crystal was studied. FEM simulations and experimental studies showed both coherently and dissipatively coupled magnon-photon modes, revealing high prospects of this hybrid structure for quantum technology.

2021 - Transmission Spectroscopy of Molecular Spin Ensembles in the Dispersive Regime [Articolo su rivista]
Bonizzoni, C.; Ghirri, A.; Nakazawa, S.; Nishida, S.; Sato, K.; Takui, T.; Affronte, M.
abstract

The readout in the dispersive regime is originally developed—and it is now largely exploited—for non-demolitive measurement of super- and semiconducting qubits. More recently it has been successfully applied to probe collective spin excitations in ferro(i)magnetic bulk samples or collections of paramagnetic spin centers embedded into microwave cavities. The use of this readout technique within a semiclassical limit of excitation is only marginally investigated although it holds for a wide class of problems, including advanced magnetic resonance techniques. In this work, the coupling between a coplanar microwave resonator and diphenyl-nitroxide organic radical diluted in a fully deuterated benzophenone single crystal is investigated. Two-tone transmission spectroscopy experiments demonstrate the possibility to reconstruct the spectrum of the spin system with little loss of sensitivity with respect to the resonant regime. Likewise, pulse sequences of detuned microwave frequency allow the measurement of the spin-lattice relaxation time (T1). The independent tunability of the probe and the drive power enables one to adjust the signal-to-noise ratio of the spectroscopy. These results suggest that electron spin dispersive spectroscopy can be used as a complementary tool of electron spin resonance to investigate the spin response.

2020 - Storage and retrieval of microwave pulses with molecular spin ensembles [Articolo su rivista]
Bonizzoni, C.; Ghirri, A.; Santanni, F.; Atzori, M.; Sorace, L.; Sessoli, R.; Affronte, M.
abstract

Hybrid architectures combining complementary quantum systems will be largely used in quantum technologies and the integration of different components is one of the key issues. Thanks to their long coherence times and the easy manipulation with microwave pulses, electron spins hold a potential for the realization of quantum memories. Here, we test diluted oxovanadium tetraphenyl porphyrin (VO(TPP)) as a prototypical molecular spin system for the Storage/Retrieval of microwave pulses when embedded into planar superconducting microwave resonators. We first investigate the efficiency of several pulse sequences in addressing the spins. The Carr-Purcell and the Uhrig Dynamical Decoupling enhance the memory time up to three times with three π pulses. We then successfully store and retrieve trains of up to 5 small pulses by using a single recovery pulse. These results demonstrate the memory capabilities of molecular spin ensembles when embedded into quantum circuits.

2019 - Towards quantum sensing with molecular spins [Articolo su rivista]
Troiani, F.; Ghirri, A.; Paris, M. G. A.; Bonizzoni, C.; Affronte, M.
abstract

Molecular spins have shown genuine quantum properties, both as collections of independent units and as individual objects. Their properties and performances can be engineered at molecular level, while advanced technologies to coherently manipulate magnetic objects and to address them with unprecedented spatial and energy resolution have emerged in the last years. Here we address the question on how to exploit quantum features of molecular spins for quantum sensing. To this end, we summarise some basic ideas and discuss some examples where molecular spins can play a role in the field.

2018 - Coherent coupling of molecular spins with microwave photons in planar superconducting resonators [Articolo su rivista]
Bonizzoni, Claudio; Ghirri, Alberto; Affronte, Marco
abstract

Within the quest for solid state quantum systems to be used for fundamental as well as applied research, molecular spins have recently emerged as a versatile platform with interesting performances in terms of quantum coherence and correlation. Molecular units provide well defined environment to electronic spins and they represent elementary bricks for complex nano-architectures and nano-devices. Here we review our recent efforts and results on their efficient integration in circuit Quantum ElectroDynamics and, more specifically, in reaching their coherent coupling with microwave photons in planar resonators. To monitor molecular spin performances over a wide temperature and magnetic field range we have first developed microwave planar resonators made of high Tc superconductors, obtaining excellent performances up to liquid Nitrogen temperature and in magnetic fields up to 7 Tesla. Ensembles of different molecular spins systems are then systematically tested. The regime of high spin-photon cooperativity is achieved with molecular spins diluted in nonmagnetic matrix at 0.5 K, while the strong coupling regime is observed with concentrated samples of organic radicals up to 50 K. The possibility to create coherent states among distinct spin ensembles is further explored in similar spectroscopic experiments. These results show that molecular spins can be efficiently integrated in quantum devices.

2018 - Microwave dual-mode resonators for coherent spin-photon coupling [Articolo su rivista]
Bonizzoni, C.; Troiani, F.; Ghirri, A.; Affronte, M.
abstract

We implement superconducting Yttrium barium copper oxide planar resonators with two fundamental modes for circuit quantum electrodynamics experiments. We first demonstrate good tunability in the resonant microwave frequencies and in their interplay, as emerges from the dependence of the transmission spectra on the device geometry. We then investigate the magnetic coupling of the resonant modes with bulk samples of 2,2-diphenyl-1-picrylhydrazyl organic radical spins. The transmission spectroscopy performed at low temperature shows that the coherent spin-photon coupling regime with the spin ensembles can be achieved by each of the resonator modes. The analysis of the results within the framework of the input-output formalism and by means of entropic measures demonstrates coherent mixing of the degrees of freedom corresponding to two remote spin ensembles and, with a suitable choice of the geometry, the approaching of a regime with spin-induced mixing of the two photon modes.

2018 - Radical-lanthanide ferromagnetic interaction in a TbIII bis-phthalocyaninato complex [Articolo su rivista]
Komijani, Dorsa; Ghirri, Alberto; Bonizzoni, Claudio; Klyatskaya, Svetlana; Moreno-Pineda, Eufemio; Ruben, Mario; Soncini, Alessandro; Affronte, Marco; Hill, Stephen
abstract

Recent studies have highlighted the importance of organic ligands in the field of molecular spintronics, via which delocalized electron-spin density can mediate magnetic coupling to otherwise localized 4f moments of lanthanide ions, which show tremendous potential for single-molecule device applications. To this end, highfield/ high-frequency electron paramagnetic resonance (EPR) spectroscopy is employed to study a neutral terbium bis-phthalocyaninato metalorganic complex, [TbPc2]0, with the aim of understanding the magnetic interaction between the Ising-like moment of the lanthanide ion and the unpaired spin density on the coordinating organic radical ligand. Themeasurements were performed on a previously unknown[TbPc2]0 structural phase crystallizing in the Pnma space group. EPR measurements on powder samples of [TbPc2]0 reveal an anisotropic spectrum, which is attributed to the spin- 1 2 radical coupled weakly to the EPR-silent TbIII ion. Extensive double-axis rotation studies on a single crystal reveal two independent spin- 1 2 signals with differently oriented (albeit identical) uniaxial g-tensors, in complete agreement with x-ray structural studies that indicate two molecular orientations within the unit cell. The easy-axis nature of the radical EPR spectra thus reflects the coupling to the Ising-like TbIII moment. This is corroborated by studies of the isostructural [YPc2]0 analog (where Y is nonmagnetic yttrium), which gives a completely isotropic radical EPR signal. The experimental results for the terbium complex are well explained on the basis of an effective model that introduces a weak ferromagnetic Heisenberg coupling between an isotropic spin- 1/2 and an anisotropic spin-orbital moment, J = 6, that mimics the known, strong easy-axis Tb · · · Pc2 crystal-field interaction.

2017 - Coherent coupling between Vanadyl Phthalocyanine spin ensemble and microwave photons: Towards integration of molecular spin qubits into quantum circuits [Articolo su rivista]
Bonizzoni, C.; Ghirri, A.; Atzori, M.; Sorace, L.; Sessoli, Roberta; Affronte, M.
abstract

Electron spins are ideal two-level systems that may couple with microwave photons so that, under specific conditions, coherent spin-photon states can be realized. This represents a fundamental step for the transfer and the manipulation of quantum information. Along with spin impurities in solids, molecular spins in concentrated phases have recently shown coherent dynamics under microwave stimuli. Here we show that it is possible to obtain high cooperativity regime between a molecular Vanadyl Phthalocyanine (VOPc) spin ensemble and a high quality factor superconducting YBa2Cu3O7 (YBCO) coplanar resonator at 0.5 K. This demonstrates that molecular spin centers can be successfully integrated in hybrid quantum devices.

2016 - Coherently coupling distinct spin ensembles through a high-Tc superconducting resonator [Articolo su rivista]
Ghirri, Alberto; Bonizzoni, Claudio; Troiani, Filippo; Buccheri, N.; Beverina, L.; Cassinese, A.; Affronte, Marco
abstract

The problem of coupling multiple spin ensembles through cavity photons is revisited by using (3,5-dichloro-4- pyridyl)bis(2,4,6-trichlorophenyl) methyl (PyBTM) organic radicals and a high-T-c superconducting coplanar resonator. An exceptionally strong coupling is obtained and up to three spin ensembles are simultaneously coupled. The ensembles are made physically distinguishable by chemically varying the g factor and by exploiting the inhomogeneities of the applied magnetic field. The coherent mixing of the spin and field modes is demonstrated by the observed multiple anticrossing, along with the simulations performed within the input-output formalism, and quantified by suitable entropic measures.

2016 - Coupling molecular spin centers to microwave planar resonators: towards integration of molecular qubits in quantum circuits [Articolo su rivista]
Bonizzoni, Claudio; Ghirri, Alberto; Bader, K.; Van Slageren, J.; Perfetti, M.; Sorace, L.; Lan, Y.; Fuhr, O.; Ruben, M.; Affronte, Marco
abstract

We present spectroscopic measurements looking for the coherent coupling between molecular magnetic centers and microwave photons. The aim is to find the optimal conditions and the best molecular features to achieve the quantum strong coupling regime, for which coherent dynamics of hybrid photon-spin states take place. To this end, we used a high critical temperature YBCO superconducting planar resonator working at 7.7 GHz and at low temperatures to investigate three molecular mononuclear coordination compounds, namely (PPh4)2[Cu(mnt)2] (where mnt2- = maleonitriledithiolate), [ErPc2]-TBA+ (where pc2- is the phtalocyaninato and TBA+ is the tetra-n-butylammonium cation) and Dy(trensal) (where H3trensal = 2,2′,2′′-tris(salicylideneimino)triethylamine). Although the strong coupling regime was not achieved in these preliminary experiments, the results provided several hints on how to design molecular magnetic centers to be integrated into hybrid quantum circuits.

2015 - Microstrip Resonators and Broadband Lines for X-band EPR Spectroscopy of Molecular Nanomagnets [Articolo su rivista]
Ghirri, Alberto; Bonizzoni, Claudio; Righi, Mattia; Fedele, Federico; Timco, Grigore; Winpenny, Richard; Affronte, Marco
abstract

We present a practical setup to perform continuous-wave X-band electron paramagnetic resonance spectroscopy by using planar microstrip lines and general purpose instrumentation. We fabricated Ag/alumina and Nb/sapphire microstrip resonators and transmission lines and compared their performance down to 2 K and under applied magnetic field. We used these devices to study single crystals of molecular Cr3 nanomagnets. By means of X-band planar resonators we measured angle-dependent spectra at fixed frequency, while broadband transmission lines were used to measure continuous wave spectra with varying frequency in the range 2–25 GHz. The spectra acquired at low temperatures allowed to extract the essential parameters of the low-lying energy levels of Cr3 and demonstrate that this method is particularly suitable to study small crystals of molecular nanomagnets.

2015 - YBa2Cu3O7 microwave resonators for strong collective coupling with spin ensembles [Articolo su rivista]
Ghirri, Alberto; Bonizzoni, Claudio; Gerace, D.; Sanna, S.; Cassinese, A.; Affronte, Marco
abstract

Coplanar microwave resonators made of 330 nm-thick superconducting YBa2Cu3O7 have been realized and characterized in a wide temperature (T, 2–100 K) and magnetic field (B, 0–7 T) range. The quality factor (QL) exceeds 104 below 55K and it slightly decreases for increasing fields, remaining 90% of QLðB ¼ 0Þ for B¼7 T and T¼2K. These features allow the coherent coupling of resonant photons with a spin ensemble at finite temperature and magnetic field. To demonstrate this, collective strong coupling was achieved by using di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium organic radical placed at the magnetic antinode of the fundamental mode: the in-plane magnetic field is used to tune the spin frequency gap splitting across the single-mode cavity resonance at 7.75 GHz, where clear anticrossings are observed with a splitting as large as 82 MHz at T¼2K. The spin-cavity collective coupling rate is shown to scale as the square root of the number of active spins in the ensemble.