As the accuracy of a measurement approaches the uncertainty limit set by quantum mechanics, the results become dependent on the dynamics of the interaction between the measuring device and the system. This finding may explain why quantum experiments often produce conflicting results and may contradict basic assumptions about physical reality.

#### Analyze research and results

Two quantum physicists from Hiroshima University recently analyzed the dynamics of a gauge interaction, in which the value of a physical property is determined by a quantum change in the state of a gauge. This is a difficult problem, because quantum theory does not determine the value of a physical property unless the system is in what is called the “eigenstate” of that physical property, which is a very small set of special quantum states for which the physical property has the property. Fixed value.

Researchers have solved this fundamental problem by combining information about a system’s past with information about its future in describing the system’s dynamics during a measurement interaction, showing that the observable values of a physical system depend on the measurement dynamics. The interaction by which this is observed.

The team recently published the results of their study in the journal *Physical review research*.

“There is a lot of disagreement about the interpretation of quantum mechanics because different experimental results cannot be reconciled with the same physical reality,” said Holger Hoffmann, a professor at the Graduate School of Advanced Science and Engineering at Hiroshima University in Hiroshima, Japan.

“In this paper, we study how quantum superpositions in the dynamics of a measurement interaction shape the observed reality of a system seen in the meter response. This is a big step toward explaining the meaning of ‘superposition’ in quantum mechanics,” said Hofmann.

#### Superposition and physical reality

In quantum mechanics, superposition describes a situation in which two possible realities appear to coexist, even though they can be clearly distinguished when the appropriate measurement is made. Analysis of the team’s study suggests that superpositions describe different types of reality when different measurements are made. The reality of an object depends on the object’s interactions with its surrounding environment.

“Our results show that the physical reality of an object cannot be separated from the context of all its interactions with the environment, past, present and future, providing strong evidence against the widespread belief that our world can be reduced to a mere composition of objects.” “Physical building blocks,” Hoffman said.

According to quantum theory, the gauge shift representing the value of the physical property observed in the measurement depends on the dynamics of the system resulting from the back action fluctuations by which the gauge disturbs the state of the system. Quantum superpositions between different possible system dynamics shape the response of the measuring device and assign specific values to it.

The authors further explained that fluctuations in the system’s dynamics depend on the strength of the gauge interaction. In the limit of weak interactions, the fluctuations of the system’s dynamics are negligible and the counter shift can be determined from the Hamilton-Jacobi equation, a classical differential equation that expresses the relationship between a physical property and its associated dynamics.

When the measurement interaction is stronger, complex quantum interference effects between different system dynamics are observed. Fully resolved measurements require a completely random distribution of the system’s dynamics. This corresponds to the superposition of all possible system dynamics, where quantum interference effects determine only those components of the quantum process that correspond to the eigenvalues of the physical property.

Eigenvalues are the values assigned by school quantum mechanics to measurement results – exact Photon Numbers, spin up or down, etc. As the new results show, these values are the result of a completely random distribution of the dynamics. Different values must be taken into account when the system dynamics are not completely random by analogy.

#### Implications for understanding quantum measurements

Interestingly, this observation provides a new perspective for using measurement results to describe reality. It is commonly assumed that local particles or integer spin values are measurement-independent elements of reality, but these research results indicate that these values are only generated by quantum interferences in sufficiently strong measurements. Our understanding of the meaning of empirical data may need fundamental revision.

Hoffman and his team look forward to further clarifying the contradictory results observed in many quantum experiments. “Context-dependent facts can explain a wide range of seemingly contradictory quantum effects. We are now working on better explanations for these phenomena. Ultimately, the goal is to develop a more intuitive understanding of the fundamental concepts of quantum mechanics that avoids misunderstandings caused by “Naive belief in the reality of microscopic objects.”

Reference: “Dependence of measurement results on the dynamics of coherent quantum interactions between the system and the scale” by Tomonori Matsushita and Holger F. Hoffmann, 31 July 2023, *Physical review research*.

DOI: 10.1103/PhysRevResearch.5.033064

The study was funded by the Japan Science and Technology Agency.

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