Researchers Boost Quantum States to Near 100% Fidelity

The creation of nonclassical states of light, particularly those with a large number of photons, represents a significant challenge in quantum science, yet these states are crucial for advancements in quantum computing and precision measurement. Chen-yi Zhang and Jun Jing, from the School of Physics at Zhejiang University, alongside their colleagues, now present a new method for efficiently generating these complex states. Their research details a measurement-based protocol that uses interactions between light and matter, specifically employing a carefully timed series of measurements on an atom to filter and refine the light’s quantum properties. This approach offers a potentially faster and less resource-intensive pathway to creating high-fidelity nonclassical states, scaling favourably compared to existing techniques and opening doors to more powerful quantum technologies, including enhanced sensing capabilities.

The method involves a generalized parity measurement constructed through multiple rounds of free-evolution and measurement with precisely timed intervals, which efficiently filters unwanted population and conditionally directs the target mode towards a desired Fock state. In ideal conditions, a Fock state can be prepared with a fidelity exceeding 98% using only eight rounds of measurements, and remains effective even with imperfections such as qubit dissipation, dephasing, and cavity decay.

Sequential Measurements Generate Quantum Superpositions

This research introduces a novel method for generating and manipulating quantum states, specifically Dicke states and arbitrary Fock state superpositions, using sequential generalized measurements. This approach offers potential advantages in terms of efficiency and fidelity compared to traditional methods, and demonstrates the feasibility of high-fidelity state preparation with implications for quantum metrology, computation, and information processing.

Fock States Created Via Atomic Filtering

Researchers have developed a new method for creating specific quantum states of light, known as Fock states, which are valuable resources for advanced information processing and precise measurements. This approach utilizes a carefully orchestrated series of interactions between light and an ancillary atom, combined with repeated measurements of the atom’s state, effectively filtering out unwanted photon numbers and guiding the light towards the desired Fock state. The number of measurements required to create a large Fock state scales logarithmically with the target photon number, offering a substantial advantage over other state preparation methods. Beyond creating Fock states, the researchers also showed that their method can generate more complex quantum states known as Dicke states, useful for enhancing the precision of measurements and achieving performance suitable for advanced metrology applications.

Fock State Preparation via Atomic Measurement

The research presents a new method for preparing specific quantum states of light, known as Fock states, valuable for advanced technologies like quantum information processing and precision measurement. This method involves interacting a beam of light with an ancillary atom and performing sequential measurements on the atom to gradually “filter” the light into the desired Fock state, utilizing a generalized parity measurement achieved through repeated interactions and measurements. The results demonstrate that this method can prepare Fock states with high fidelity, requiring a number of measurement rounds that scales logarithmically with the target state’s energy level, and extends to generating complex quantum states known as Dicke states, useful for enhancing the precision of certain measurements. The authors acknowledge that imperfections in real-world quantum systems affect performance, but report achieving high fidelity Fock states even with these limitations, suggesting further improvements in system stability would enhance performance.