Generation Of Temporal Multimode Squeezed States Of Femtosecond Pulse Light

Non-classical light field is not only a fundamental issue in physics but also plays a significant role in quantum information processing.It is an indispensable resource in modern quantum communication,information confidentiality,quantum measurement etc.Compared to non-classical single-mode field,non-classical multimode light field can contain more information,greatly expand the channel capacity in quantum communication to improve the transmission rate and communication security.At present,the study of multimode non-classical light field is mainly around space mode and time-frequency mode,especially the non-classical light field of optical orbit angular momentum mode,which has become an important research hotspot in quantum information,and produced a lot of important results.Compared with the spatial mode,the time domain mode can be naturally compatible with waveguide technology making them more efficient use of existing single-mode fiber networks.And they are not susceptible to stationary or slowly varying medium perturbations such as linear dispersion,due to their overlapping spectra,making them more suitable for fiber networks applications.Distinguished from conventional time-or frequency-based optical multiplexing,which use separated short pulses to define different information channels,the use of temporal multi-mode for channel multiplexing is intrinsically based on genuinely orthogonal wave-packet modes,which provide in-principle zero cross talk between mode channels.In addition,we can achieve ultra-high precision quantum clock synchronization program based on the time domain multi-mode squeezed light.Based on the importance of time-domain multimode non-classical light field,this paper mainly focuses on the experimental generation of temporal multimode femtosecond pulse squeezed states.The key parts include the following:1)The experimental generation of temporal multimode squeezed states of femtosecond pulse light.Firstly,we analyze the theory of generating and measuring pulsed squeezed light generated from a SPOPO.Using a degenerate synchronous pump optical parametric oscillator(SPOPO)with a type-? nonlinear crystal,we obtain the temporal multimode squeezed light.Then,a 4f pulse shaping device was inserted into the light path of the BHD Local field.We manipulate output pulse shapes of the Local field by loading the suitable function on the SLM to match the supermode produced in the SPOPO,and complete the measurement of temporal multimode squeezed light.In the experiment,the pump power is 175 mw,we directly observed the squeezing of the leading five temporal “super-mode” at the analysis frequency of 1.2MHz.The squeezing level was about-2.0 d B(amplitude quadrature);-1.0 d B(phase quadrature);-0.7 d B(amplitude quadrature);-0.4 d B(phase quadrature);-0.1 d B(amplitude quadrature).2)In order to further expand the multimode optical field dimension,combined with the advantages of time domain mode and spatial mode,we study the experimental generation of femtosecond pulse squeezed state with spatial mode TEM01.Based on the experiment of temporal multimode squeezed states,we introduce a small tilt in the front of the SPOPO to produce the TEM01 mode,also in the Local field.In the experiment,the pump power is 130 m W,we observed-0.7 d B of the amplitude quadrature squeezing with high-order TEM01 transverse mode at the analysis frequency of 1.2MHz.