Chapter 1: Understanding Time Crystals

The concept of a "time crystal" emerged from groundbreaking research conducted within Google's Sycamore chip, which operates at extremely low temperatures within a cryostat. A team of researchers at Google has successfully created and verified the existence of a time crystal using a quantum computer. This achievement has garnered significant attention in the specialized press, with some claiming it could revolutionize physics by challenging the second law of thermodynamics. Let's delve deeper into this fascinating topic.

The term "time crystal," formally referred to by researchers as “Time-Crystalline Eigenstate Order,” represents a recent advancement in the field. The idea was first proposed in 2012 by Nobel Prize winner Frank Wilczek, who suggested the existence of a novel state of matter—a “crystal of time.”

Regular crystals, as we know them, consist of a matrix of particles or molecules arranged in a repeating, ordered structure exhibiting translational symmetry. In contrast, a time crystal maintains the repetitive aspect, but instead of a spatial structure, it repeats its configuration at specific intervals over time.

To create a time crystal, one must prevent the typical behavior of a system, wherein energy exchange leads to heat generation due to interactions among the system's components. Instead, external influences must be applied to generate a periodic response, allowing the system to revert to its original state after a predetermined number of cycles. Essentially, a time crystal oscillates, returning to its initial configuration at regular intervals.

Chapter 2: Google’s Contribution to Time Crystal Research

So, what groundbreaking work did the Google researchers accomplish?

When the time crystals were initially created in 2016 and 2017, it was speculated they could be integrated into quantum computers. Unlike conventional computers that process information in binary (0s and 1s), quantum computers utilize qubits, enabling superposition—where a qubit can represent both 0 and 1 simultaneously.

This unique property allows researchers to evaluate whether the quantum state of the system has been maintained, assess the accuracy of the results, and determine if the outcomes align with theoretical expectations. However, a significant challenge in quantum computing is decoherence, which occurs when a system interacts with nearby particles, leading to the loss of its quantum behavior.

Google's quantum computer, which utilizes superconducting qubits, has a coherence period of only 50 microseconds. Thus, calculations must be limited to this brief window to avoid losing the desired quantum state.

Instead of focusing on spin like the diamond experiments, Google researchers examined the order of values within many-body systems. When qubits are placed in an equilibrium state, lower energy states exhibit order, while higher energy states display disorder. Under typical circumstances, introducing excessive energy results in disorder.

However, certain systems can achieve “many-body localization,” which allows for local conservation and a limited number of ordered states. Google researchers directed microwave pulses to their quantum chip; if the qubits do not absorb heat or release energy to their surroundings, they can undergo multiple transitions between ordered states. With sufficient pulses, the system can revert to its original state.

This achievement allowed the team to restore the quantum system to its initial state every two microwave pulses, effectively demonstrating the existence of a time crystal through a quantum computer. While it is necessary to inject energy into the system using electromagnetic pulses, the time crystal can return to its original state, even amid minor imperfections in the qubits' state changes, without compromising the quantum state due to thermal instabilities.

In conclusion, this remarkable feat does not violate the second law of thermodynamics, as that law pertains to closed systems—unlike the open systems involved in this research.