Add rust crate for the providers interface in Qiskit (#15892)

This commit adds a new crate to the qiskit crate collection for defining
the BackendV3 interface in Qiskit. The backendv3 interface will be a
Rust first construct that will expose a shared interface to both Python
and C, while the current BackendV2 interface is only exposed to Python.
As a first step to facilitate it's development this commit adds a new
empty crate where we'll slowly build up the functionality of that
interface. Right now it's just empty but in subsequent commits we'll add
onto it.

Author: mtreinish

Cargo.lock

@@ -58,6 +58,7 @@ qiskit-cext = { path = "crates/cext" }
 qiskit-cext-vtable = { path = "crates/cext-vtable" }
 qiskit-circuit = { path = "crates/circuit" }
 qiskit-circuit-library = { path = "crates/circuit_library" }
+qiskit-providers = { path = "crates/providers" }
 qiskit-qasm2 = { path = "crates/qasm2" }
 qiskit-qasm3 = { path = "crates/qasm3" }
 qiskit-qpy = { path = "crates/qpy" }

Cargo.toml

@@ -30,6 +30,8 @@ The intention is that (much) longer term, we might be wanting to expose more of
 * `qiskit-synthesis` is the crate for synthesis functionality.
 * `qiskit-circuit-library` is the crate for circuit library functions. It contains constructors or other
   circuit functionality that builds on the core circuit data model defined in `qiskit-circuit`.
+* `qiskit-providers` is the crate that defines the providers interface for Qiskit. The providers interface is what defines the concept of a Backend.
+  The backend models a quantum computer, which is the QPU and the infrastructure around it required to execute circuits on the quantum computer.
 * `qiskit-util` is for small utility functions and data structures that are independent of all
   Qiskit-specific objects, so it can be depended-on by both `quantum-info` and `circuit`.
 

crates/README.md

@@ -0,0 +1,14 @@
+[package]
+name = "qiskit-providers"
+version.workspace = true
+edition.workspace = true
+rust-version.workspace = true
+license.workspace = true
+
+[lib]
+name = "qiskit_providers"
+
+[dependencies]
+
+[lints]
+workspace = true

crates/providers/Cargo.toml

@@ -0,0 +1,4 @@
+# `qiskit-providers`
+
+This crate defines the Rust data structures and core providers interface
+for Qiskit.

crates/providers/README.md

@@ -0,0 +1,11 @@
+// This code is part of Qiskit.
+//
+// (C) Copyright IBM 2026
+//
+// This code is licensed under the Apache License, Version 2.0. You may
+// obtain a copy of this license in the LICENSE.txt file in the root directory
+// of this source tree or at https://www.apache.org/licenses/LICENSE-2.0.
+//
+// Any modifications or derivative works of this code must retain this
+// copyright notice, and modified files need to carry a notice indicating
+// that they have been altered from the originals.