Two-colour quantum entanglement in a singly resonant optical parametric oscillator approaching threshold

Following the analytical work of Ref. [1], a numerical analysis of squeezing and quantum entanglement in a continuous wave singly-resonant optical parametric oscillator approaching threshold is provided. The singly resonant case is mainly relevant to largely non-degenerate signal and idler modes (two-colour output). As the threshold of oscillation is approached the numerical spectra of the intensity difference confirm squeezing of quantum fluctuations and a progressive line-narrowing in the linear case. In the nonlinear case entanglement is confirmed although progressively reduced when approaching threshold with the squeezing spectra still displaying a narrowing of the spectral line. Modification of quantum entanglement approaching threshold is also evaluated via the condition of state inseparability

Self-organization, pattern formation, cavity solitons, and rogue waves in singly resonant optical parametric oscillators

The spatiotemporal dynamics of singly resonant optical parametric oscillators with external seeding displays hexagonal, roll, and honeycomb patterns, optical turbulence, rogue waves, and cavity solitons. We derive appropriate mean-field equations with a sinc2 nonlinearity and demonstrate that off-resonance seeding is necessary and responsible for the formation of complex spatial structures via self-organization. We compare this model with those derived close to the threshold of signal generation and find that back-conversion of signal and idler photons is responsible for multiple regions of spatiotemporal self-organization when increasing the power of the pump field

p85 regulatory subunit of PI3K mediates cAMP–PKA and estrogens biological effects on growth and survival

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Insight from an Italian Delphi Consensus on EVAR feasibility outside the instruction for use: the SAFE EVAR Study

BACKGROUND: The SAfety and FEasibility of standard EVAR outside the instruction for use (SAFE-EVAR) Study was designed to define the attitude of Italian vascular surgeons towards the use of standard endovascular repair (EVAR) for infrarenal abdominal aortic aneurysm (AAA) outside the instruction for use (IFU) through a Delphi consensus endorsed by the Italian Society of Vascular and Endovascular Surgery (Societa Italiana di Chirurgia Vascolare ed Endovascolare - SICVE). METHODS: A questionnaire consisting of 26 statements was developed, validated by an 18 -member Advisory Board, and then sent to 600 Italian vascular surgeons. The Delphi process was structured in three subsequent rounds which took place between April and June 2023. In the first two rounds, respondents could indicate one of the following five degrees of agreement: 1) strongly agree; 2) partially agree; 3) neither agree nor disagree; 4) partially disagree; 5) strongly disagree; while in the third round only three different choices were proposed: 1) agree; 2) neither agree nor disagree; 3) disagree. We considered the consensus reached when >70% of respondents agreed on one of the options. After the conclusion of each round, a report describing the percentage distribution of the answers was sent to all the participants. RESULTS: Two -hundred -forty-four (40.6%) Italian Vascular Surgeons agreed to participate the first round of the Delphi Consensus; the second and the third rounds of the Delphi collected 230 responders (94.3% of the first -round responders). Four statements (15.4%) reached a consensus in the first rounds. Among the 22 remaining statements, one more consensus (3.8%) was achieved in the second round. Finally, seven more statements (26.9%) reached a consensus in the simplified last round. Globally, a consensus was reached for almost half of the proposed statements (46.1%). CONCLUSIONS: The relatively low consensus rate obtained in this Delphi seems to confirm the discrepancy between Guideline recommendations and daily clinical practice. The data collected could represent the source for a possible guidelines' revision and the proposal of specific Good Practice Points in all those aspects with only little evidence available

Theory and simulations of singly resonant optical parametric oscillators

Optical parametric oscillators have been known and used for a long time as efficient sources of non-classical states of light both below threshold of oscillation, where they generate squeezed vacuum states and bi-partite entangled states, and above threshold of oscillation, where they generate intensity correlated twin beams. The singly-resonant cavity, where only one of the three field involved in the parametric amplification process is resonated (signal), is in principle a simpler configuration to realize experimentally but, to the best of our knowledge, theoretical investigations of non-classical features of the light from a singly-resonant OPO (SROPO) are missing. One of the reasons is that SROPOs operate with strongly non-degenerate frequencies while much of the literature on squeezing focuses on the degenerate or close to degeneracy cases. Recent interest in non-classical correlations of the strongly non-degenerate regime of parametric down-conversion makes the study of entanglement in SROPO important for the optimization of coherent sources with fluctuations below the shot-noise level. There are clear technical advantages for SROPO configurations: only resonance of the signal field has to be maintained, continuous temperature tuning and suppression of mode-hopping. As a matter of fact even if the doubly resonant configuration, where both the signal and the idler fields are resonated, has a much lower threshold pump power, the tuning behavior is complicated and is massively affected by changes of the crystal temperature or pump wavelength, causing the signal and idler wavelengths undergoing jumps, and the tuning is generally non-monotonous. This is because the operation wavelengths are determined primarily by the requirement for simultaneous resonance for signal and idler, and not only by a phase-matching condition as in the case of singly resonant configuration. It is in this spirit that in Chapter 4 we apply the input-output theory of optical cavities to formulate a quantum treatment of a continuous wave singly-resonant optical parametric oscillator. This case is mainly relevant to largely non-degenerate signal and idler modes. We show that both intensity and quadrature squeezing are present and that the maximum noise reduction below the standard quantum limit is the same at the signal and idler frequencies in a way similar to the doubly resonant case. As the threshold of oscillation is approached, however, the intensity-difference and quadrature spectra display a progressive line-narrowing which is absent in the balanced doubly-resonant case. By using the separability criterion for continuous variables, the signal-idler state is found to be entangled over wide ranges of the parameters. We show that attainable levels of squeezing and entanglement make singly-resonant configurations ideal candidates for two-colour quantum information processes because of their ease of tuning in experimental realizations. Another very interesting feature of SROPOs which, this time, has no counterpart in the doubly-resonant regime is described in Chapter 5 where model equations for the evolution of signal and idler pulses in a synchronously pumped optical parametric oscillator are derived and numerically integrated. A novel regime of giant sub-threshold pulses driven by quantum fluctuations is described through the analysis of stability eigenvalues, growth factors and pseudospectra. Subthreshold pulses driven by quantum fluctuations are found at various mirror reflectivities in the non degenerate regime where signal and idler have different group velocities. Giant sub-threshold pulses open the possibility of observing macroscopic continuous variable entanglement with nonclassical features. This important feature is peculiar to the singly-resonant configuration and has no counterpart in the doubly-resonant regime. Very interesting classical features of SROPOs light are investigated in Chapter 6 where we show that spatio-temporal dynamics of singly resonant optical parametric oscillators with external seeding displays hexagonal, roll and honeycomb patterns, optical turbulence, rogue waves and cavity solitons. We derive appropriate mean-field equations with a sinc² non-linearity and demonstrate that off-resonance seeding is necessary and responsible for the formation of complex spatial structures via self-organization. We compare this model with those derived close to the threshold of signal generation and find that back-conversion of signal and idler photons is responsible for multiple regions of spatio-temporal self-organization when increasing the power of the pump field.Optical parametric oscillators have been known and used for a long time as efficient sources of non-classical states of light both below threshold of oscillation, where they generate squeezed vacuum states and bi-partite entangled states, and above threshold of oscillation, where they generate intensity correlated twin beams. The singly-resonant cavity, where only one of the three field involved in the parametric amplification process is resonated (signal), is in principle a simpler configuration to realize experimentally but, to the best of our knowledge, theoretical investigations of non-classical features of the light from a singly-resonant OPO (SROPO) are missing. One of the reasons is that SROPOs operate with strongly non-degenerate frequencies while much of the literature on squeezing focuses on the degenerate or close to degeneracy cases. Recent interest in non-classical correlations of the strongly non-degenerate regime of parametric down-conversion makes the study of entanglement in SROPO important for the optimization of coherent sources with fluctuations below the shot-noise level. There are clear technical advantages for SROPO configurations: only resonance of the signal field has to be maintained, continuous temperature tuning and suppression of mode-hopping. As a matter of fact even if the doubly resonant configuration, where both the signal and the idler fields are resonated, has a much lower threshold pump power, the tuning behavior is complicated and is massively affected by changes of the crystal temperature or pump wavelength, causing the signal and idler wavelengths undergoing jumps, and the tuning is generally non-monotonous. This is because the operation wavelengths are determined primarily by the requirement for simultaneous resonance for signal and idler, and not only by a phase-matching condition as in the case of singly resonant configuration. It is in this spirit that in Chapter 4 we apply the input-output theory of optical cavities to formulate a quantum treatment of a continuous wave singly-resonant optical parametric oscillator. This case is mainly relevant to largely non-degenerate signal and idler modes. We show that both intensity and quadrature squeezing are present and that the maximum noise reduction below the standard quantum limit is the same at the signal and idler frequencies in a way similar to the doubly resonant case. As the threshold of oscillation is approached, however, the intensity-difference and quadrature spectra display a progressive line-narrowing which is absent in the balanced doubly-resonant case. By using the separability criterion for continuous variables, the signal-idler state is found to be entangled over wide ranges of the parameters. We show that attainable levels of squeezing and entanglement make singly-resonant configurations ideal candidates for two-colour quantum information processes because of their ease of tuning in experimental realizations. Another very interesting feature of SROPOs which, this time, has no counterpart in the doubly-resonant regime is described in Chapter 5 where model equations for the evolution of signal and idler pulses in a synchronously pumped optical parametric oscillator are derived and numerically integrated. A novel regime of giant sub-threshold pulses driven by quantum fluctuations is described through the analysis of stability eigenvalues, growth factors and pseudospectra. Subthreshold pulses driven by quantum fluctuations are found at various mirror reflectivities in the non degenerate regime where signal and idler have different group velocities. Giant sub-threshold pulses open the possibility of observing macroscopic continuous variable entanglement with nonclassical features. This important feature is peculiar to the singly-resonant configuration and has no counterpart in the doubly-resonant regime. Very interesting classical features of SROPOs light are investigated in Chapter 6 where we show that spatio-temporal dynamics of singly resonant optical parametric oscillators with external seeding displays hexagonal, roll and honeycomb patterns, optical turbulence, rogue waves and cavity solitons. We derive appropriate mean-field equations with a sinc² non-linearity and demonstrate that off-resonance seeding is necessary and responsible for the formation of complex spatial structures via self-organization. We compare this model with those derived close to the threshold of signal generation and find that back-conversion of signal and idler photons is responsible for multiple regions of spatio-temporal self-organization when increasing the power of the pump field