Was Crocodile stronger at Marineford? Or was he holding back in Alabasta?

 During the Alabasta arc, Crocodile displayed a level of power that was initially considered overwhelming by the Straw Hat Pirates. He possessed the Logia-type Devil Fruit called the Suna Suna no Mi (Sand-Sand Fruit), which granted him the ability to control and transform into sand. He had a reputation as a Shichibukai and controlled the desert kingdom of Alabasta from the shadows. His strength was showcased through his battles with Luffy and others. At Marineford, Crocodile was present as part of the war that took place at Marine Headquarters. While he did participate in the battle, he didn't display the same level of dominance as some other powerful characters present. This has led fans to speculate that he might not have been as strong as initially portrayed in Alabasta. It's important to note that power scaling and character abilities can be subject to interpretation and development by the author. Oda often keeps details deliberately open-ended to keep the story intriguing.

How can we use quantum mechanics to build a computer?

 Quantum mechanics can be used to build a computer by exploiting the unique properties of particles on a subatomic level, such as the principles of superposition and entanglement. These principles allow quantum computers to store and process information in a fundamentally different way than classical computers, which are based on the principles of classical mechanics.

The basic building block of a quantum computer is the quantum bit, or qubit. A qubit is a unit of quantum information that can exist in multiple states simultaneously, unlike a classical bit, which can only exist in one of two states (0 or 1). This allows a quantum computer to perform multiple calculations at the same time, which can greatly increase its computational power.

Quantum computers also use the principle of entanglement to store and manipulate large amounts of data in a much more compact form than classical computers. This is because entanglement allows multiple particles to be connected in a way that allows them to share information and influence each other's behavior, even when they are separated by large distances. This allows quantum computers to process large amounts of data more efficiently than classical computers.

To build a quantum computer, researchers use specialized techniques and materials, such as superconducting circuits or trapped ions, to create and control the quantum states of particles. This is a complex and challenging task, but if successful, it can enable the construction of a quantum computer that can perform certain operations much faster and more efficiently than a classical computer.