Physical implementation of scalable quantum architectures faces an immense challenge in form of fragile quantum states. To overcome it, quantum architectures with fault tolerance is desirable. This is achieved currently by using surface code along with a transversal gate set. This dictates the need for decomposition of universal Multi Control Toffoli (MCT) gates using a transversal gate set. Additionally, the transversal non-Clifford phase gate incurs high latency which makes it an important factor to consider during decomposition. Besides, the decomposition of large Multicontrol Toffoli (MCT) gate without ancilla presents an additional hurdle. In this manuscript, we address both of these issues by introducing Clifford+ZN gate library. We present an ancilla free decomposition of MCT gates with linear phase depth and quadratic phase count. Furthermore, we provide a technique for decomposition of MCT gates in unit phase depth using the Clifford+ZN library, albeit at the cost of ancillary lines and quadratic phase count.

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Decoherence is the greatest obstacle to the physical realization of scalable quantum computer, jeopardises coherent superposition of the qubit, and makes qubit extremely fragile. Quantum Error Correction Code (QECC), and Fault-tolerant quantum computation collectively could protect qubit and improve scalability. On the other hand, the conventional logic circuit is no more useful in quantum computing due to much difference from quantum logic. However, quantum computer has to perform classical tasks which can be addressed by translating to its equivalent quantum algorithm. Herein, zerogarbage-based reversible and fault-tolerant quantum circuit for 1 : 2, and 2 : 4 Decoder with enable signal using Clifford + T-group are proposed. Further, the design approach to implement n : 2 n decoder on fault-tolerant quantum logic in linear T − depth is extended. Besides, performance parameters likely T − count, T − depth, and garbage output have been evaluated for n : 2 n decoder. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.