From: mk_thisisit
Michał Parniak, a Polish physicist, conducts research that aims to deepen the understanding of the differences between the classical world and the quantum world [07:17:19]. His work involves creating quantum states of objects that are “somehow interesting,” often by making them macroscopic [07:33:00].
The Quantum-Classical Boundary
The quantum and classical physics differences are fundamental:
- The quantum world is described by non-intuitive laws, expressible mathematically, like the Schrödinger equation, which predicts probabilities of events in the microscopic realm [08:05:39]. However, the exact reason why these probabilities are realized remains a postulate, not fully understood [08:23:00].
- In contrast, the classical world is deterministic, governed by laws like Newton’s forces, where initial conditions can predict final conditions [08:35:08].
A central question in physics is where the boundary between these two worlds lies [08:52:00]. Scientists question at what point an object with an increasing number of particles suddenly begins to behave deterministically and entirely differently from its quantum description [08:59:02]. Experimental research focuses on trying to create quantum states of increasingly macroscopic objects to explore this interface [09:13:13].
Experimental Approaches to Bridging the Worlds
Parniak’s research and related experiments attempt to find “bridges” between the quantum and classical domains [09:59:02].
Schrödinger’s Cat Analogy
The famous thought experiment of Schrödinger’s cat illustrates this problem [10:11:06]. It questions why an atom can exist in a quantum superposition (described as quantum), but a cat, connected to this atom by a mechanism, cannot [10:37:00]. Experiments aim to scrutinize the mechanism that connects the quantum atom to the macroscopic cat, specifically looking at how a quantum object like a photon interacts with a detector and if that detector’s operation can also be described quantum mechanically [10:48:00].
Macroscopic Entanglement and Mesoscale Objects
Parniak has explored macroscopic entanglement, which is achieving quantum entanglement in larger systems. One experiment in Copenhagen entangled a mechanical membrane (a “drum”) with the spins of atoms [03:07:07]. His team in Warsaw also created different macroscopic states using their record-breaking quantum memory, entangling many photons stored in the memory [03:31:00]. This achieved a state of entanglement with an exceptionally large object, setting a record [03:54:00].
At the Nils Bohr Institute in Copenhagen, Parniak worked on introducing a small membrane, akin to a drumhead but with nanometer thickness and millimeter width, into a quantum state [11:46:00]. This object, considered “mesoscale,” had aspects like its vibration introduced into a quantum state [12:15:05]. They managed to create an interaction between it and individual photons and control this interaction [12:33:00].
A significant challenge in these studies is achieving the ground state of such mechanical oscillators [13:05:00]. By using laser cooling to reach temperatures near absolute zero, they observed that the ground state of a mechanical oscillator still contains certain quantum fluctuations [13:19:00]. These quantum fluctuations are observable even for macroscopic objects, demonstrating that quantum mechanics will not allow for infinite precision in measuring an object’s position, as it retains some movement even at absolute zero [13:41:00].
Quantum Gravity and Superposition
The bridge between the quantum and classical worlds may ultimately involve the quantum theory of gravity [14:08:00]. Current experiments, like those in Austria, are attempting to place mechanical oscillators (small balls) into a state of superposition, being in two places at once [14:33:00]. If an object is in a superposition of being in two places, it also has its own gravity [14:59:00].
The challenge lies in two areas:
- Getting an increasingly macroscopic object into a quantum state [15:21:00].
- Increasing the precision of gravity measurements to detect gravity from smaller objects [15:31:00]. The hope is that these two efforts will meet in a “middle ground” where gravity from an object in quantum superposition can be observed [15:40:00].
Quantum Metrology and Practical Applications
Quantum metrology is a practical field focused on building systems that measure things with enhanced precision [15:58:00]. It leverages “tricks” from quantum mechanics to reduce quantum noise, a technique known as “squeezing” [16:21:00]. This involves reducing fluctuations in light in one aspect at the cost of increasing them where they don’t matter [16:32:00].
These techniques are already applied in practical measurements:
- Gravitational Wave Detectors: Operating detectors like LIGO/Virgo in the US, Italy, and Japan use quantum light engineering to double the precision of gravitational wave measurements [16:45:00]. This is an example of the interplay between classical and quantum physics where concepts from quantum theory improve macroscopic detection [17:17:00].
- Measuring Position: Measurements of mirror positions face quantum limits. While increasing light can make measurements more classical and reduce fluctuations, it also disturbs the mirrors via photon pressure [17:39:00]. There is an optimum level, which can be improved using quantum mechanics tricks [18:02:00]. Every measurement has its quantum limits, determined by the fluctuations of the measurement tool and the object being measured [18:23:00].
Quantum Information and the Universe
Understanding the structure of quantum information is a key focus, bringing scientists closer to understanding how quanta work [21:50:00]. Photons are excellent “workhorses” for quantum information due to the control scientists have over them [21:21:00].
Information Encoding
The light spectrum carries information for:
- Chemical Research: Studying the composition of molecules, such as atmospheric gases [18:56:00]. Parniak’s quantum memory acts as a specific quantum processor, able to extract precise spectral lines from photons, allowing for distinguishing very close spectral lines [06:34:00].
- Telecommunications: Packing light’s degrees of freedom more efficiently to encode and decode information. This is crucial for improving transmission in optical fibers, especially for long-distance connections like transatlantic cables [19:06:00]. Researchers are inventing protocols to better decode information [20:22:00].
Limits of Encoding Information
While matter might offer unimaginably large limits for information encoding at the elementary particle level, it is not yet practically achievable [22:32:00]. For photons (visible light), information can be recorded in:
- Polarization: Associated with the photon’s spin [23:09:00].
- Temporal Degree of Freedom: For example, a single photon existing in a superposition of being in two distinct light pulses [23:22:00].
Future Directions and Astronomical Applications
Future experiments aim to create more universal devices for similar quantum protocols across various light wavelengths, beyond just infrared light [24:00:00].
Black Hole Imaging
The device used to image the black hole, creating the famous image, is not a direct photo but a visualization created by superimposing images from microwave detectors placed globally [24:23:00]. This technique, which can also be applied in the optical domain, allows for imaging tiny objects by effectively using the entire Earth as a “lens” [24:36:00]. Parniak’s team is exploring if their device can perform more precise microwave measurements or extract more information using single photons, potentially leading to a more accurate image of a black hole’s event horizon [25:29:00]. Extending these detectors into space could further increase the “lens” size to the entire solar system [26:07:00].
Cosmic Microwave Background (CMB)
Microwaves can also help understand other cosmic structures, such as the cosmic microwave background (CMB) radiation [26:16:00]. This radiation is a remnant of the Big Bang, found everywhere, and its fluctuations can reveal many features of the universe [26:23:00]. While not strictly quantum physics, the goal to measure these microwaves more precisely provides a strong motivation for Parniak’s research, alongside motivations like improving communication networks [27:05:00].