Periodic Reporting for period 1 - STORMYTUNE (Spectral-Temporal Metrology with Tailored Quantum Measurements)
Reporting period: 2020-10-01 to 2022-03-31
Metrology explores the most efficient and precise way to perform measurements. This established area of study has considerable impact on our everyday lives. A GPS would not work without the capability to measure distances precisely, and spectral fingerprinting is an established technique to identify, e.g. drugs and hazardous materials. In recent years, researchers have begun to study metrology in the counterintuitive realm of quantum mechanics, so called quantum metrology. Surprisingly – or maybe not so, depending on whom you ask – it turns out that quantum properties such as entanglement can be highly beneficial for metrological tasks. Experiments have shown measurement precision beyond any classical measurement and to date, ever more demonstrations are reaching the ultimate precision limits set by quantum mechanics. These findings have two potential impacts: on the one hand, we can imagine measurements that simply cannot be implemented with classical means and that consequently enable hitherto unknown applications; on the other hand, we find that a better measurement can reach the same precision as a worse measurement in less time, leading to faster data acquisition. Interestingly, quantum metrology mainly focusses on measuring phases, with only few works considering spatial imaging. There is no comprehensive approach to measuring time or frequency using quantum mechanical methods, although many applications could benefit from such techniques.
This is where the work of STORMYTUNE comes in. We will develop a theoretical and experimental toolbox for time-frequency quantum metrology and explore possible avenues for improving applications using our methods. In contrast to other approaches to quantum metrology that mainly focus on using fragile probe states, we will investigate the achievable benefits when using quantum measurements and simple, robust probe states. Further, we aim to improve the performance of our techniques by adding the ideas of superresolution measurements and compressed sensing to time-frequency quantum metrology, thus reducing measurement times even more.
The STORMYTUNE consortium comprises world-leading scientists and industry partners, who are ideally positioned to achieve the project goals. For this research, we have identified three strategic objectives that will guide our efforts.
- Objective 1: Develop a time-frequency quantum metrology toolbox that comprises of the tools and methods for investigating the limits of temporal and spectral measurements using quantum mechanics.
- Objective 2: Investigate the limits of time-frequency quantum metrology with regards to the ultimate measurement precision, the resource consumption, and the ease of implementation.
- Objective 3: Implement proof-of-concept demonstrations that show a clear benefit of quantum metrology when compared to standard measurements and that exploit techniques from superresolution measurements and compressed sensing.
This is where the work of STORMYTUNE comes in. We will develop a theoretical and experimental toolbox for time-frequency quantum metrology and explore possible avenues for improving applications using our methods. In contrast to other approaches to quantum metrology that mainly focus on using fragile probe states, we will investigate the achievable benefits when using quantum measurements and simple, robust probe states. Further, we aim to improve the performance of our techniques by adding the ideas of superresolution measurements and compressed sensing to time-frequency quantum metrology, thus reducing measurement times even more.
The STORMYTUNE consortium comprises world-leading scientists and industry partners, who are ideally positioned to achieve the project goals. For this research, we have identified three strategic objectives that will guide our efforts.
- Objective 1: Develop a time-frequency quantum metrology toolbox that comprises of the tools and methods for investigating the limits of temporal and spectral measurements using quantum mechanics.
- Objective 2: Investigate the limits of time-frequency quantum metrology with regards to the ultimate measurement precision, the resource consumption, and the ease of implementation.
- Objective 3: Implement proof-of-concept demonstrations that show a clear benefit of quantum metrology when compared to standard measurements and that exploit techniques from superresolution measurements and compressed sensing.
We have built quantum detectors that are used in our laboratories to measure temporal and spectral properties with precisions at the ultimate quantum limit. This means that there are no better detectors, nor will there be better detectors. Our devices are doing the best job allowed by quantum mechanics. Why can we say that? Because we have also developed the underlying theoretical description. We can use the language of quantum information science to formulate the problems we are looking into. From this we derive the ultimate precision limit, which we then compare to our measurement results. At present, STORMYTUNE partners have build four different experiments in as many countries that are continuously taking data, while our theory is identifying new promising application scenarios that can benefit from quantum metrology.
We are also using our theory to investigate the ultimate measurement precision for different scenarios. Here, we take special care to consider experimental imperfections. These may reduce the achievable precision and we are working out just how imperfect our experiments can afford to be without losing the quantum benefit.
Finally, we have demonstrated a quantum advantage in measurement precision in several scenarios. We have performed a so-called multi-parameter estimation experiment, where we tried to simultaneously measure the timing separation, the joint arrival time, and the intensity difference of two light pulses. Although this sounds highly academical, such scenarios are of general interest as they describe the application of measuring backscattered light. This can, for instance, occur in material testing, where light pulses are used to probe the uniformity of a surface. We succeeded in identifying and realizing measurements that allowed us to extract all three parameters with quantum-limited precision. We also had a first go at adding compressed sensing techniques to these measurements. As an example, we were interested in reconstructing the spectral and temporal content of an unknown light pulse with as few measurements as possible. Typically, compressed sensing requires some knowledge about the object under investigations. Our methods forego this knowledge and allow us to characterize unknown light pulses quickly and efficiently. Finally, we have measured the noise of commercial laser systems with a precision beyond standard noise measurements. Lasers are an important part of today’s economy and being able to characterize them better of faster is interesting from both a science and application point of view.
We are also using our theory to investigate the ultimate measurement precision for different scenarios. Here, we take special care to consider experimental imperfections. These may reduce the achievable precision and we are working out just how imperfect our experiments can afford to be without losing the quantum benefit.
Finally, we have demonstrated a quantum advantage in measurement precision in several scenarios. We have performed a so-called multi-parameter estimation experiment, where we tried to simultaneously measure the timing separation, the joint arrival time, and the intensity difference of two light pulses. Although this sounds highly academical, such scenarios are of general interest as they describe the application of measuring backscattered light. This can, for instance, occur in material testing, where light pulses are used to probe the uniformity of a surface. We succeeded in identifying and realizing measurements that allowed us to extract all three parameters with quantum-limited precision. We also had a first go at adding compressed sensing techniques to these measurements. As an example, we were interested in reconstructing the spectral and temporal content of an unknown light pulse with as few measurements as possible. Typically, compressed sensing requires some knowledge about the object under investigations. Our methods forego this knowledge and allow us to characterize unknown light pulses quickly and efficiently. Finally, we have measured the noise of commercial laser systems with a precision beyond standard noise measurements. Lasers are an important part of today’s economy and being able to characterize them better of faster is interesting from both a science and application point of view.
During the first part of STORMYTUNE, we have developed an extensive theory framework, which expands the limits of our understanding of quantum metrology. We have built novel devices that allow phase-sensitive time-frequency measurements that reach the ultimate precision, even in real-world experiments. Until the end of the project we expect to demonstrate several relevant use cases. A combination of superresolution and comressive sensing will be a helpful tool for the characterization of complex quantum systems, allowing for experimental access to system sizes that are currently beyond reach. We expect this to become a standard tool for novel quantum technologies that aim at scaling systems, such as photonic quantum computation and simulation. Our methods of extracting the maximum information from incomplete data can be of interest to other scientific disciplines that are limited by low signal levels or require the highest possible precision. Examples include astronomy, gravitational wave sensing, and fundamental tests of general relativity. STORMYTUNE can potentially help to advance progress in these disciplines and thus advance science as such.