Squeezed states of light are essential for emerging quantum technology in metrology and information processing. Chip-integrated photonics offers a route to scalable and efficient squeezed light generation, however, parasitic nonlinear processes and optical losses remain significant challenges. Here, we demonstrate single-mode quadrature squeezing in a photonic crystal microresonator via degenerate dual-pump spontaneous four-wave mixing. Implemented in a scalable, low-loss silicon-nitride photonic-chip platform, the microresonator features a tailored nano-corrugation that modifies its resonances to suppress parasitic nonlinear processes. In this way, we achieve an estimated 7.8 dB of on-chip squeezing in the bus waveguide, with potential for further improvement. These results open a promising pathway toward integrated squeezed light sources for quantum-enhanced interferometry, Gaussian boson sampling, coherent Ising machines, and universal quantum computing.Squeezed states of light are essential for emerging quantum technology in metrology and information processing. Chip-integrated photonics offers a route to scalable and efficient squeezed light generation, however, parasitic nonlinear processes and optical losses remain significant challenges. Here, we demonstrate single-mode quadrature squeezing in a photonic crystal microresonator via degenerate dual-pump spontaneous four-wave mixing. Implemented in a scalable, low-loss silicon-nitride photonic-chip platform, the microresonator features a tailored nano-corrugation that modifies its resonances to suppress parasitic nonlinear processes. In this way, we achieve an estimated 7.8 dB of on-chip squeezing in the bus waveguide, with potential for further improvement. These results open a promising pathway toward integrated squeezed light sources for quantum-enhanced interferometry, Gaussian boson sampling, coherent Ising machines, and universal quantum computing.

arXiv:2502.17337Jan 1, 20251 citation

Chip-integrated single-mode coherent-squeezed light source using four-wave mixing in microresonators

Patrick Tritschler, Torsten Ohms, Christian Schweikert +7 more

Squeezed light constitutes a key resource for quantum optical technologies including quantum sensing, computing, communication and metrology. For many applications the generation of squeezed light typically requires at least two nonlinear optical stages involving careful phase and frequency matching to achieve the required mixing of squeezed and coherent light. In our work, we introduce an on-chip system that simplifies the generation of coherent-squeezed light, utilizing only a single squeezing stage. We achieve this by pumping a silicon nitride ( $\mathrm{Si_3N_4}$ ) microring resonator to produce single-mode squeezed light through four-wave mixing at the same frequency as the pump mode, leveraging the inherent $χ^{(3)}$ -nonlinearity of the $\mathrm{Si_3N_4}$ resonator. Our on-chip system demonstrates a squeezing of -4.7 dB with a clear perspective towards -10 dB squeezing. We also provide a theoretical model that describes the straightforward yet robust generation of single-mode squeezing at the injection locking point of the ring resonator. In fact, we show that a design with a normal dispersion can be used for robust generation of bright squeezed light without the need for careful suppression of unwanted nonlinear processes. Overall, our findings highlight an approach which drastically simplifies the generation of coherent-squeezed light in photonic integrated circuits.Squeezed light constitutes a key resource for quantum optical technologies including quantum sensing, computing, communication and metrology. For many applications the generation of squeezed light typically requires at least two nonlinear optical stages involving careful phase and frequency matching to achieve the required mixing of squeezed and coherent light. In our work, we introduce an on-chip system that simplifies the generation of coherent-squeezed light, utilizing only a single squeezing stage. We achieve this by pumping a silicon nitride ($\mathrm{Si_3N_4}$) microring resonator to produce single-mode squeezed light through four-wave mixing at the same frequency as the pump mode, leveraging the inherent $χ^{(3)}$-nonlinearity of the $\mathrm{Si_3N_4}$ resonator. Our on-chip system demonstrates a squeezing of -4.7 dB with a clear perspective towards -10 dB squeezing. We also provide a theoretical model that describes the straightforward yet robust generation of single-mode squeezing at the injection locking point of the ring resonator. In fact, we show that a design with a normal dispersion can be used for robust generation of bright squeezed light without the need for careful suppression of unwanted nonlinear processes. Overall, our findings highlight an approach which drastically simplifies the generation of coherent-squeezed light in photonic integrated circuits.

arXiv:2502.16278Feb 22, 20250 citations

Nanophotonic source of broadband quadrature squeezing

Robert Čerňanský, Alberto Politi

Squeezed light are optical beams with variance below the Shot Noise Level. They are a key resource for quantum technologies based on photons, they can be used to achieve better precision measurements, improve security in quantum key distribution channels and as a fundamental resource for quantum computation. To date, the majority of experiments based on squeezed light have been based on non-linear crystals and discrete optical components, as the integration of quadrature squeezed states of light in a nanofabrication-friendly material is a challenging technological task. Here we measure 0.45 dB of GHz-broad quadrature squeezing produced by a ring resonator integrated on a Silicon Nitride photonic chip that we fabricated with CMOS compatible steps. The result corrected for the off-chip losses is estimated to be 1 dB below the Shot Noise Level. We identify and verify that the current results are limited by excess noise produced in the chip, and propose ways to reduce it. Calculations suggest that an improvement in the optical properties of the chip achievable with existing technology can develop scalable quantum technologies based on light.Squeezed light are optical beams with variance below the Shot Noise Level. They are a key resource for quantum technologies based on photons, they can be used to achieve better precision measurements, improve security in quantum key distribution channels and as a fundamental resource for quantum computation. To date, the majority of experiments based on squeezed light have been based on non-linear crystals and discrete optical components, as the integration of quadrature squeezed states of light in a nanofabrication-friendly material is a challenging technological task. Here we measure 0.45 dB of GHz-broad quadrature squeezing produced by a ring resonator integrated on a Silicon Nitride photonic chip that we fabricated with CMOS compatible steps. The result corrected for the off-chip losses is estimated to be 1 dB below the Shot Noise Level. We identify and verify that the current results are limited by excess noise produced in the chip, and propose ways to reduce it. Calculations suggest that an improvement in the optical properties of the chip achievable with existing technology can develop scalable quantum technologies based on light.

arXiv:1904.07283Apr 15, 20192 citations

Degenerate squeezing in a dual-pumped integrated microresonator: Parasitic processes and their suppression

Hossein Seifoory, Z. Vernon, Dylan H. Mahler +3 more

Using a general Hamiltonian treatment, we theoretically study the generation of degenerate quadrature squeezing in a dual-pumped integrated microring resonator coupled to a waveguide. Considering a dual-pump four-wave mixing configuration in an integrated ${\text{Si}}_{3}{\text{N}}_{4}$ platform, and following the coupled-mode theory approach, we investigate the effects of parasitic quantum nonlinear optical processes on the generation of squeezed light. Considering five resonance modes in this approach allows us to include the most important four-wave mixing processes involved in such a configuration. We theoretically explore the effects of the pump detunings on different nonlinear processes and show that the effects of some of the parasitic processes are effectively neutralized by symmetrically detuning the two pumps. This yields a significant enhancement in the output squeezing quality without physically changing the structure, but suffers from the trade-off of requiring substantially higher pump power for a fixed target level of squeezing.Using a general Hamiltonian treatment, we theoretically study the generation of degenerate quadrature squeezing in a dual-pumped integrated microring resonator coupled to a waveguide. Considering a dual-pump four-wave mixing configuration in an integrated ${\text{Si}}_{3}{\text{N}}_{4}$ platform, and following the coupled-mode theory approach, we investigate the effects of parasitic quantum nonlinear optical processes on the generation of squeezed light. Considering five resonance modes in this approach allows us to include the most important four-wave mixing processes involved in such a configuration. We theoretically explore the effects of the pump detunings on different nonlinear processes and show that the effects of some of the parasitic processes are effectively neutralized by symmetrically detuning the two pumps. This yields a significant enhancement in the output squeezing quality without physically changing the structure, but suffers from the trade-off of requiring substantially higher pump power for a fixed target level of squeezing.

arXiv:2109.03298Physical Review AMar 28, 202227 citations

Near-Degenerate Quadrature-Squeezed Vacuum Generation on a Silicon-Nitride Chip

Yun Zhao, Yoshitomo Okawachi, Jae K. Jang +3 more

Squeezed states are a primary resource for continuous-variable (CV) quantum information processing. To implement CV protocols in a scalable and robust way, it is desirable to generate and manipulate squeezed states using an integrated photonics platform. In this Letter, we demonstrate the generation of quadrature-phase squeezed states in the radio-frequency carrier sideband using a small-footprint silicon-nitride microresonator with a dual-pumped four-wave-mixing process. We record a squeezed noise level of 1.34 dB (±0.16 dB) below the photocurrent shot noise, which corresponds to 3.09 dB (±0.49 dB) of quadrature squeezing on chip. We also show that it is critical to account for the nonlinear behavior of the pump fields to properly predict the squeezing that can be generated in this system. This technology represents a significant step toward creating and manipulating large-scale CV cluster states that can be used for quantum information applications, including universal quantum computing.Squeezed states are a primary resource for continuous-variable (CV) quantum information processing. To implement CV protocols in a scalable and robust way, it is desirable to generate and manipulate squeezed states using an integrated photonics platform. In this Letter, we demonstrate the generation of quadrature-phase squeezed states in the radio-frequency carrier sideband using a small-footprint silicon-nitride microresonator with a dual-pumped four-wave-mixing process. We record a squeezed noise level of 1.34 dB (±0.16 dB) below the photocurrent shot noise, which corresponds to 3.09 dB (±0.49 dB) of quadrature squeezing on chip. We also show that it is critical to account for the nonlinear behavior of the pump fields to properly predict the squeezing that can be generated in this system. This technology represents a significant step toward creating and manipulating large-scale CV cluster states that can be used for quantum information applications, including universal quantum computing.

arXiv:2002.01082Physical Review LettersMay 12, 2020188 citations

Single-Mode Squeezed Light Generation via χ(3) Nonlinearity in Integrated Fabry-Perot Bragg Grating Microresonators

Ruijian Wang

Squeezed light, a non-classical state characterized by reduced quantum fluctuations in one field quadrature, is a key resource for improving precision measurements and quantum metrology. In the past decades, the most well-known application of squeezed light is in gravitational wave detection, realized by the Laser Interferometer Gravitational- Wave Observatory (LIGO). There, squeezing has pushed the strain precision of a 4-km-long interferometer to an astounding level below 10−23 1/√Hz. An interesting question we are pursuing is whether squeezing and related improvements in precision can be realized in cm-size photonic chips. Recently, the Kerr nonlinearity on integrated photonics chips has opened a new window for squeezed light generation in a nanophotonic platform. In this thesis, we seek to extend these advances to single-mode squeezed state (SMS) generation in Silicon Nitride (SiN) Fabry-Perot Bragg Grating (FPBG) microresonators with a coherent-laser-based dual-pump SMS scheme. This is the first step towards a robust and scalable approach of on-chip squeezed-light sources for a new class of integrated photonics sensors.Squeezed light, a non-classical state characterized by reduced quantum fluctuations in one field quadrature, is a key resource for improving precision measurements and quantum metrology. In the past decades, the most well-known application of squeezed light is in gravitational wave detection, realized by the Laser Interferometer Gravitational- Wave Observatory (LIGO). There, squeezing has pushed the strain precision of a 4-km-long interferometer to an astounding level below 10−23 1/√Hz. An interesting question we are pursuing is whether squeezing and related improvements in precision can be realized in cm-size photonic chips. Recently, the Kerr nonlinearity on integrated photonics chips has opened a new window for squeezed light generation in a nanophotonic platform. In this thesis, we seek to extend these advances to single-mode squeezed state (SMS) generation in Silicon Nitride (SiN) Fabry-Perot Bragg Grating (FPBG) microresonators with a coherent-laser-based dual-pump SMS scheme. This is the first step towards a robust and scalable approach of on-chip squeezed-light sources for a new class of integrated photonics sensors.

Nov 3, 20250 citations

\mathrm{Si_3N_4}

) microring resonator to produce single-mode squeezed light through four-wave mixing at the same frequency as the pump mode, leveraging the inherent

χ^{(3)}

-nonlinearity of the

\mathrm{Si_3N_4}

resonator. Our on-chip system demonstrates a squeezing of -4.7 dB with a clear perspective towards -10 dB squeezing. We also provide a theoretical model that describes the straightforward yet robust generation of single-mode squeezing at the injection locking point of the ring resonator. In fact, we show that a design with a normal dispersion can be used for robust generation of bright squeezed light without the need for careful suppression of unwanted nonlinear processes. Overall, our findings highlight an approach which drastically simplifies the generation of coherent-squeezed light in photonic integrated circuits.

{\text{Si}}_{3}{\text{N}}_{4}

platform, and following the coupled-mode theory approach, we investigate the effects of parasitic quantum nonlinear optical processes on the generation of squeezed light. Considering five resonance modes in this approach allows us to include the most important four-wave mixing processes involved in such a configuration. We theoretically explore the effects of the pump detunings on different nonlinear processes and show that the effects of some of the parasitic processes are effectively neutralized by symmetrically detuning the two pumps. This yields a significant enhancement in the output squeezing quality without physically changing the structure, but suffers from the trade-off of requiring substantially higher pump power for a fixed target level of squeezing.