Quantum Sensing in Action

Introduction

Sensors are essential for living beings to survive. Machines and computers also have sensors to detect their surrounding environment. In place of human senses, they employ detectors to perceive the world.

Classical sensors are utilized for detecting and measuring physical properties in the real world, like temperature, light, motion, or pressure. They convert these analog signals into digital data, which allows us to keep track of, manage, and make informed decisions in various applications. These sensors form the basis of a multitude of technologies that enhance our daily lives, from thermostats and security systems to weather stations and medical devices, by providing valuable information for efficiency, safety, and convenience.

In the other hand, Quantum sensors, which utilize the principles of quantum mechanics (quantum measurement, quantum coherence, and entanglement), are a relatively recent development in the field of sensing technology.

They have gained significant attention and are still in the process of being further developed and refined for various applications. The motivation behind the quantum sensors technology, either improve performance and/or smaller SWaP (i.e., Size, Weight and Power).

Types of Quantum Sensors

Recently, a new category of applications has emerged that utilizes quantum mechanical systems as sensors for various physical quantities (such as magnetic and electric fields, rotations, time and frequency, temperature, and pressure). These sensors are known as “quantum sensors” and take advantage of the high sensitivity of quantum systems to external disturbances. Interestingly, this trend in quantum technology is similar to the history of semiconductors, where sensors such as light meters based on selenium photocells found commercial applications many years before computers.

Quantum sensing is a relatively new area of research in the field of quantum science and engineering. However, a lot of the concepts utilized in this field have already been established and are familiar to the physics community. These concepts have been developed over several decades, primarily in high-resolution spectroscopy, particularly in atomic physics and magnetic resonance.

Quantum sensing is either using a tiny quantum object (tiny object can be something like an individual electron, a single atom, or a small group of atoms, such as those found in superconducting or spin qubits, trapped ions, or neutral atoms) to measure the energy levels of electrons, magnets, or vibrations in very small particles, or using quantum coherence, a wave-like property, to measure other physical quantities. Additionally, quantum entanglement, a spooky connection between two objects, can be used to make measurements incredibly precise. All of these techniques are like using a super tiny ruler or like ripples in water to measure very small things or to measure with a high level of accuracy respectively.

DiVincenzo criteria:

Similar to the DiVincenzo criteria used for quantum computation, there are four essential attributes needed for a quantum system to operate as a quantum sensor. These attributes consist of the three initial DiVincenzo criteria :

State Preparation: The first criterion of a quantum system is that it possesses distinct and discernible energy levels. More precisely, we will consider it as a system consisting of two energy levels (or a collection of such two-level systems). These two levels are characterized by a lower energy state represented as |0? and an upper energy state represented as |1?. These states are distinguished by the energy difference between them, denoted as the transition energy.

Initialization: the ability to set the quantum system into a familiar state at the start and to later retrieve and determine its state accurately.

External interaction: when a quantum system interacts with a physical parameter such as gravity or electric and magnetic fields, it causes changes in the energy levels or the speed at which transitions happen between these levels. To be effective, sensors should have a strong interaction with the external signal they are targeting and maintain long decoherence times. High-quality sensors meet these requirements.

Communication: in quantum sensing means that the quantum system can send and receive quantum information (signals V), represented as “flying qubits.” These flying qubits serve as a means for the quantum sensor to exchange signals with other systems or devices.

Quantum sensors exhibit an impressive range of capabilities when it comes to making precise measurements in diverse fields of science and technology. They can discern the subtleties of electric fields using tools such as atomic electric field sensors and solid-state defects. In the realm of time and frequency measurements, quantum sensors, particularly atomic clocks, stand as unparalleled standards of accuracy. When it comes to magnetic fields, quantum sensors offer solutions in the form of atomic magnetometers, superconducting magnetometers, and solid-state defects.

Additionally, quantum sensors play a pivotal role in measuring acceleration due to gravity through atomic gravimeters and superconducting gravitometers. Atomic gradiometers: By cooling atoms with a laser, the atoms are divided into two parts and then released to fall freely. After this, the two parts are combined again. Because of gravity, the two beams are affected differently and this difference can be measured through their interference pattern. The versatility of quantum sensors in these domains has opened new frontiers in precision measurement and scientific exploration.

Conclusion

Quantum sensing is an innovative field of scientific exploration that is driven by the pursuit of precision and sensitivity. Motivated by the need to unlock deeper insights into our world, these quantum sensors have the potential to revolutionize industries from healthcare to environmental monitoring. The combination of quantum technologies and sensing holds the promise of uncovering new breakthroughs that could lead to a new era of innovation and discovery. Quantum sensing is not merely a tool; it’s a testament to the limitless possibilities of the quantum realm.