Continuous wave multimode entanglement

• Through type II optical parametrical process with orbital momentum, the astigmation between HG01 and HG10 modes induced by nonlinear crystal is eliminated, thus HG01 and HG10 modes with different polarizations simultaneously resonant in the cavity. Based on a single type II phase-matching optical parametrical oscillator with eliminated astigmation, two couples of cw entanglements with different spatial modes are experimentally generated.
• Firstly obtain cw hyper-entanglement of 0.7 dB simultaneously with spin and orbital momentum entanglement.

Direct measurement of orbital angular momentum states

• Proposed and experimentally demonstrated a direct measurement scheme of orbital Stokes parameters combining an asymmetric Mach–Zehnder interferometer with an extra Dove prism in one arm. It has some advantages in distant quantum information transmission as there is no need for local light.

Cw spatial GHZ entanglement

• Experimentally prepared cw hyper-entanglement, realizing simultaneous entanglement of two dimensions (polarization and orbital momentum); generated multimode GHZ entanglement in single optical cavity.

Higher order mode entanglement enhancement

• With optimal pump mode, we enhanced the entanglement of high-order modes, providing good nonclassical source for high-order and high-dimension entanglement.

Rotation measurement beyond the standard quantum limit

• With OAM squeezed light, we realized rotation angle measurement beyond standard quantum limit, obtaining a precision-enhancement of a factor of 1.4.

Small-displacement measurement beyond standard quantum limit

• With universal method, generated spatial squeezed light with the quantum noise smaller than shot noise limit and realized optical beam’s transverse small-displacement measurement beyond classical limit and the corresponding minimum measurable displacement is 0.99 Å.

Small-displacement and tilt measurement based on high-order modes

• Presented the scheme of displacement measurement with high-order Hermite-Gauss modes, theoretically proved that the higher mode order, the more measurement pricision. Experimentlly demonstrated small-displacement based on TEM10 signal beam, obtaining 1.41-fold precision compared to traditional TEM00 signal mode.

• With optimal local mode, experimentally demonstrated Cramer-Rao bound limited small displacement and tilt measurement of high-order mode.

Low-frequency (audio-frequency) signal measurement

• Presented a method of combining usual broadband squeezed light and two-frequency laser. Transfer high-frequency quantum noise to low-frequency region and utilize high-frequency entangled sidebands of squeezing to perform sub-shot-noise measurement of a low-frequency signal.
  

• Experimentally generated 7 dB squeezed light at low-frequency band of 20 kHz and realized 3 dB signal-to-noise ratio (SNR) enhancement beyond standard quantum limit.
  

Temporal multimode femto-second pulse squeezing and temporal measurement

• Used mode-locked femto-second pulsed laser to pump the synchronously pumped optical parametric oscillator and generated pulsed quadrature squeezing of 2 dB, up to the international level (1.2 dB). With the pulse shaper, generated local light of time-domain super-mode and measured the corresponding super-mode squeezing of several orders generated by SPOPO using balanced homodyne detection. This time-domain multimode nonclassical optical fields can be used to generate compact and scalable multipartite entangled states and applied into quantum communication and computation.

Measurement of wave-particle duality and quantum uncertainty

• Firstly studied the relation between the wave-particle duality and quantum uncertainty from pure state to mixed state and analyzed the variation relation of wave property and particle property.

High-order wave-particle duality

• Studied the relation of high-order wave-particle duality and quantum uncertainty in the two-photon state.
• Based on the single-photon pure state and mixed state measurement, further in the multi-photon condition, introduced two new operators of high-order visibility and high-order distinguishability and experimentally studied the relation of two-photon first order and second order wave-particle duality, extending the relation of optical wave-particle duality.