New methods for generating and characterising multimode squeezed light expand continuous-variable quantum technologies. The work focuses on type-0 and type-II optical parametric amplifiers (OPAs), investigating how variations in local oscillator (LO) profile affect measured levels of squeezing. Employing pulse shaping techniques alongside Schmidt-mode theory enables deeper insight into optimising homodyne detection of complex quantum states. Techniques for generating and assessing complex states of light applicable to continuous-variable quantum technologies have been refined; these systems rely on manipulating multiple modes simultaneously.

The team addressed inaccuracies arising during measurement due to misalignment within optical setups. Understanding how such misalignments impact results aims to improve reliability in future quantum computers and communication networks based upon continuous variables. Advances in generating and analysing complex states of light for use in emerging quantum technologies exist, with these continuous-variable systems requiring manipulation across multiple modes simultaneously.

Researchers at the Russian Quantum Centre tackled inaccuracies arising during measurement caused by misalignment within optical setups, aiming to improve reliability for future quantum computers and communication networks. Their work centres on creating ‘squeezed states of light’, where uncertainty is reduced in one property, like focusing all energy into pushing something in one direction while allowing it to wobble freely elsewhere. This generation relies upon an optical parametric amplifier (OPA), a device that creates correlated pairs of photons with specific properties akin to an electronic signal booster but specifically designed for light.

Multimode squeezing overcomes noise limits via advanced modelling and observation

Scientists from Russian Quantum Centre, alongside collaborators at M.V. Lomonosov Moscow State University and Moscow Institute of Physics and Technology, have achieved multimode squeezing exceeding a common-mode rejection ratio (CMRR) of 52.4 dB. This represents an improvement over prior methods hampered by local oscillator mismatches during detection.

Accurate measurement demanded precise matching between light modes but was often unattainable due to practical limitations within optical setups; the new threshold allows characterisation of complex quantum states previously obscured by noise. Pulse shaping techniques combined with Schmidt-mode theory enabled detailed analysis dependent on spectral profiles through both theoretical modelling and experimental characterisation of these sources.

Work at Russian Quantum Centre details how they characterised multimode squeezed light generated using optical parametric amplifiers (OPAs), observing joint spectral intensities for type-0 and type-II processes. Analysis utilising Schmidt decomposition revealed the structure of these quantum states, breaking down complex light into a series of simpler components called Schmidt modes which allowed precise behaviour modelling.

The team then replicated these theoretically predicted modes experimentally via pulse shaping applied to the local oscillator, the reference beam used for detection, employing spatial light modulators and verifying results with an optical spectrum analyser; this process provided essential spectral control over squeezing during homodyne detection.

A detailed characterisation offers a pathway towards more complex continuous variable quantum technologies because manipulating multiple modes simultaneously promises major advances in both computation and communication. Tangible improvements within actual ‘multimode quantum protocols’ remain elusive despite refining methods to account for local oscillator mismatches during detection. Nevertheless, acknowledging that immediate practical gains are not yet available does not diminish the importance of this work as careful analysis establishes a key baseline understanding. Ultrafast pumping within an optical parametric amplifier generates states where certain properties of light are more precisely defined than usual. Creating correlated pairs of photons when pumped by a laser underpinned the experimental work; theoretical modelling using Schmidt-mode theory, which decomposes complex states into simpler components akin to analysing chords in music, revealed how local oscillator profiles impact measured levels of squeezing.

The researchers demonstrated control over multimode squeezed light generated via type-0 and type-II optical parametric amplifiers. This level of spectral control during homodyne detection is important because accurately matching the profile between the signal mode and local oscillator improves characterisation of these quantum states. The study provides detailed insight into multimode squeezing that supports further development of continuous variable quantum technologies.

👉 More information
🗞 Multimode squeezed light generation and characterization
✍️ Alexander Chudakov, Vladislav Severin, Anastasia Poshevkina, Danil Malyshev, Kirill Kuznetsov, Olga Tikhonova, Dmitry Kalashnikov and Polina Sharapova
🧠 ArXiv: https://arxiv.org/abs/2609.08591

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