BigInt and xor

[Dennis Ritchie via Digitalmars-d-learn]

Tell me, please, how can I replace this code?

import std.conv : to;
import std.bigint : BigInt;
import std.string : format;
import std.stdio : writeln;

void main() {

        BigInt[10] bitArr;

        ulong n = 18_446_724_073_709_551_614U;

        bitArr[0] = format("%b", n).to!BigInt;

        writeln(bitArr[0]);
        writeln(bitArr[0] ^ 1); // not work

}

Output:
1111111111111111111011011100111101100011000110101011111111111110
1111111111111111111011011100111101100011000110101011111111111111