Qubes OS is a Linux based security-oriented and open-source operating system for personal computers. The team at Invisible Things Project has announced the official release of Qubes 3.0 (Version 3), which is now based on Hypervisor Abstraction Layer (HAL), Xen 4.4 virtualization technology and supports Debian Linux. Qubes is often misunderstood as a Linux distribution, but instead it can be called as Xen distribution. It is a Native or Bare-Metal Hypervisor that uses a microkernel framework and offer services that allow multiple operating systems to execute on the same computer hardware simultaneously.
Source: https://thehackernews.com/2015/10/secure-operating-system.html