Fusion based quantum computing

Abstract

A method includes receiving a plurality of quantum systems, wherein each quantum system of the plurality of quantum system includes a plurality of quantum sub-systems in an entangled state, and wherein respective quantum systems of the plurality of quantum systems are independent quantum systems that are not entangled with one another. The method further includes performing a plurality of joint measurements on different quantum sub-systems from respective ones of the plurality of quantum systems, wherein the joint measurements generate joint measurement outcome data and determining, by a decoder, a plurality of syndrome graph values based on the joint measurement outcome data.

What is claimed is: 
     
         1 . A method comprising:
 receiving, by a qubit fusion system, a plurality of quantum systems, wherein each quantum system of the plurality of quantum system includes a plurality of quantum sub-systems in an entangled state, and wherein respective quantum systems of the plurality of quantum systems are independent quantum systems that are not entangled with one another;   performing, by the qubit fusion system, a plurality of joint measurements on different quantum sub-systems from respective ones of the plurality of quantum systems, wherein the joint measurements generate joint measurement outcome data; and   determining, by a decoder, a plurality of syndrome graph values based on the joint measurement outcome data.   
     
     
         2 . The method of  claim 1 , wherein performing the joint measurements includes performing fusion operations. 
     
     
         3 . The method of  claim 1 , wherein performing the joint measurements include performing a destructive joint measurement via a Type II fusion operation. 
     
     
         4 . The method of  claim 1 , wherein performing the plurality of joint measurements on different quantum sub-systems from respective ones of the plurality of quantum systems includes performing the plurality of joint measurements on only a subset of the plurality of quantum sub-systems that are received by the qubit fusion system thereby resulting in a subset of unmeasured quantum sub-systems. 
     
     
         5 . The method of  claim 4 , further comprising, receiving, by the qubit fusion system, a second plurality of quantum systems, wherein each quantum system of the second plurality of quantum system includes a second plurality of quantum sub-systems in an entangled state, and wherein respective quantum systems of the second plurality of quantum systems are independent quantum systems that are not entangled with one another;
 receiving the subset of unmeasured quantum sub-systems; and   performing, by the qubit fusion system, a second plurality of joint measurements between i) second quantum sub-systems from respective ones of the plurality of second quantum systems and ii) respective quantum sub-systems from the subset of unmeasured quantum sub-systems, wherein the second plurality of joint measurements generate second joint measurement outcome data.   
     
     
         6 . A system comprising:
 a qubit fusion system comprising a plurality of fusion gates, wherein the qubit fusion system is configured to receive a plurality of quantum systems, wherein each quantum system of the plurality of quantum system includes a plurality of quantum sub-systems in an entangled state, and wherein respective quantum systems of the plurality of quantum systems are independent quantum systems that are not entangled with one another;   wherein the plurality of fusion gates are each configured to perform a joint measurement on different quantum sub-systems from respective ones of the plurality of quantum systems, wherein the joint measurements generate joint measurement outcome data; and   a decoder communicatively coupled to the qubit fusion system and configured to receive the joint measurement outcome data and to determine a plurality of syndrome graph values based on the joint measurement outcome data.   
     
     
         7 . The system of  claim 6 , wherein the fusion gates include a photonic circuit and the plurality of quantum systems comprise photons as the quantum sub-systems, wherein the photonic circuit comprises a Type II fusion gate. 
     
     
         8 . The system of  claim 6 , wherein the joint measurement comprises a two-particle projective measurement onto a Bell basis. 
     
     
         9 . The system of  claim 6 , further comprising a quantum memory, coupled to at least one the qubit fusion system and that receive and store a subset of the plurality of quantum sub-systems. 
     
     
         10 . The system of  claim 9 , wherein the quantum memory is an optical fiber. 
     
     
         11 . The system of  claim 9 , wherein the quantum memory is coupled to the qubit fusion system such that the joint measurement is performed between i) quantum sub-systems from respective ones of the plurality of quantum systems and ii) respective quantum sub-systems from the subset of the plurality of quantum sub-systems that are stored in the quantum memory. 
     
     
         12 . The system of  claim 6  further comprising a qubit entangling system that is configured to generate the plurality of quantum systems. 
     
     
         13 . The system of  claim 12 , wherein the qubit entangling system includes a quantum gate array. 
     
     
         14 . The system of  claim 13 , wherein qubit entangling system includes a photon source system that is optically connected to an entangled state generator. 
     
     
         15 . The system of  claim 14 , wherein the entangled state generator is configured to receive output photons from the photon source system and convert the output photons to an entangled photonic state. 
     
     
         16 . The system of  claim 15 , wherein the qubit entangling system includes a plurality of output waveguides that are optically coupled to the qubit fusion system and are configured to provide the entangled photonic state to inputs of the fusion gates.