<s>
The	O
One	B-Device
Clean	I-Device
Qubit	I-Device
model	O
of	O
computation	O
is	O
performed	O
an	O
qubit	O
system	O
with	O
one	O
pure	O
state	O
and	O
maximally	O
mixed	O
states	O
.	O
</s>
<s>
It	O
's	O
described	O
by	O
the	O
density	O
matrix	O
,	O
where	O
I	O
is	O
the	O
identity	B-Algorithm
matrix	I-Algorithm
.	O
</s>
<s>
In	O
computational	O
complexity	O
theory	O
,	O
DQC1	O
;	O
also	O
known	O
as	O
the	O
Deterministic	O
quantum	O
computation	O
with	O
one	B-Device
clean	I-Device
qubit	I-Device
is	O
the	O
class	O
of	O
decision	O
problems	O
solvable	O
by	O
a	O
one	B-Device
clean	I-Device
qubit	I-Device
machine	O
in	O
polynomial	O
time	O
,	O
upon	O
measuring	O
the	O
first	O
qubit	O
,	O
with	O
an	O
error	O
probability	O
of	O
at	O
most	O
1/poly	O
( n	O
)	O
for	O
all	O
instances	O
.	O
</s>
<s>
Given	O
a	O
state	O
,	O
the	O
Hadamard	B-Device
test	I-Device
can	O
estimate	O
where	O
is	O
the	O
probability	O
that	O
the	O
measured	O
clean	O
qubit	O
is	O
0	O
.	O
mixed	O
state	O
inputs	O
can	O
be	O
simulated	O
by	O
letting	O
be	O
chosen	O
uniformly	O
at	O
random	O
from	O
computational	O
basis	O
states	O
.	O
</s>
